Electron shell

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Electron shell

An electron shell may be crudely thought of as an orbit

ORBit

ORBit is a Common Object Request Broker Architecture 2.4 compliant Object Request Broker . It features mature C , C++ and Python bindings, and less developed bindings for Perl, Lisp , Pascal , Ruby , and Tcl....
followed by electrons around an atom

Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
nucleus

Atomic nucleus

The nucleus of an atom is the very dense region, consisting of nucleons , at the center of an atom. Although the size of the nucleus varies considerably according to the mass of the atom, the size of the entire atom is comparatively constant....
. Because each shell can contain only a fixed number of electrons, each shell is associated with a particular range of electron energy, and thus each shell must fill completely before electrons can be added to an outer shell. The electrons in the outermost shell determine the chemical properties of the atom (see Valence shell

Valence electron

In science, valence electrons are the electrons contained in the outermost, or valence, electron shell of an atom. Valence electrons are important in determining how an chemical element reacts chemically with other elements: The fewer valence electrons an atom holds, the less reactivity it becomes and the more likely it is to chemical rea...
).

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History

The existence of electron shells was first observed experimentally in Charles Barkla's and Henry Moseley

Henry Moseley

Henry Gwyn Jeffreys Moseley was an England physics. His main contributions to science were the quantitative justification of the previously empirical concept of atomic number, and Moseley's law....
's X-ray

X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequency in the range 30 Hertz to 30 Hertz and energies in the range 120 Electron volt to 120 keV....
absorption studies. Barkla labeled them with the letters K, L, M, N, O, P, and Q. The origin of this terminology was alphabetic. A J series was also suspected, though later experiments indicated that the K absorption lines are produced by the innermost electrons. These letters were later found to correspond to the n-values

Principal quantum number

In atomic physics, the principal quantum number symbolized as n is the firstof a set of quantum numbers of an atomic orbital. The quantum number n labels the energy levels of hydrogenic atoms....
1, 2, 3, etc. They are used in the spectroscopic Siegbahn notation

Siegbahn notation

The Siegbahn notation is used in X-ray spectroscopy to name the spectrometry that are characteristic to elements. It was created by Manne Siegbahn....
.

The name for electron shells is derived from the Bohr model

Bohr model

In atomic physics, the Bohr model created by Niels Bohr depicts the atom as a small, positively charged atomic nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity....
, in which groups of electrons were believed to orbit the nucleus at certain distances, so that their orbits formed "shells" around the nucleus.

The physical chemist Gilbert Lewis was responsible for much of the early development of the theory of the participation of valence shell electrons in chemical bonding. Linus Pauling

Linus Pauling

Linus Carl Pauling was an United States scientist, peace activist, author and list of educators. He was one of the most influential chemists in history and ranks among the most important scientists in any field of the 20th century....
later generalized and extended the theory while applying insights from quantum mechanics

Quantum mechanics

Quantum mechanics is a set of principles underlying the most fundamental known description of all physical systems at the microscopic scale . Notable amongst these principles are both a dual wave-like and particle-like behavior of matter and radiation, and prediction of probabilities in situations where classical physics predicts certaintie...
.

Shells

The electron shells are labelled K, L, M, N, O, P, and Q; or 1, 2, 3, 4, 5, 6, and 7; going from innermost shell outwards. Electrons in outer shells have higher average energy and travel further from the nucleus than those in inner shells, making them more important in determining how the atom reacts chemically and behaves as a conductor because the pull of the atom's nucleus upon them is weaker and more easily broken. In this way, a given element's reactivity is highly dependant on the electronic configuration it has.

Subshells

Each shell is composed of one or more subshells, which are themselves composed of atomic orbital

Atomic orbital

An atomic orbital is a mathematical function that describes the wave-like behavior of an electron in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus....
s. For example, the first (K) shell has one subshell, called "1s"; the second (L) shell has two subshells, called "2s" and "2p"; the third shell has "3s", "3p", and "3d"; and so on. The various possible subshells are shown in the following table:

Subshell label	l Azimuthal quantum number The Azimuthal quantum number symbolized as l is a quantum number for an atomic orbital that determines its orbital angular momentum. The azimuthal quantum number is the second of a set of quantum numbers which describe the unique quantum state of an electron and is designated by the letter l....	Max electrons	Shells containing it	Historical name
s	0	2	Every shell	sharp
p	1	6	2nd shell and higher	principal
d	2	10	3rd shell and higher	diffuse
f	3	14	4th shell and higher	fundamental
g	4	18	5th shell and higher
h	5	22	6th shell and higher
i	6	26	7th shell and higher

The first column is the "subshell label", a lowercase-letter label for the type of subshell. For example, the "4s subshell" is a subshell of the fourth (N) shell, with the type ("s") described in the first row.
The second column is the azimuthal quantum number
Azimuthal quantum number

The Azimuthal quantum number symbolized as l is a quantum number for an atomic orbital that determines its orbital angular momentum. The azimuthal quantum number is the second of a set of quantum numbers which describe the unique quantum state of an electron and is designated by the letter l....
of the subshell. The precise definition involves quantum mechanics
Quantum mechanics

Quantum mechanics is a set of principles underlying the most fundamental known description of all physical systems at the microscopic scale . Notable amongst these principles are both a dual wave-like and particle-like behavior of matter and radiation, and prediction of probabilities in situations where classical physics predicts certaintie...
, but it is a number that characterizes the subshell.
The third column is the maximum number of electrons that can be put into a subshell of that type. For example, the top row says that each s-type subshell ("1s", "2s", etc.) can have at most two electrons in it.
The fourth column says which shells have a subshell of that type. For example, looking at the top two rows, every shell has an s subshell, while only the second shell and higher have a p subshell (i.e., there is no "1p" subshell).
The final column gives the historical origin of the labels s, p, d, and f. They come from early studies of atomic spectral line
Atomic spectral line

In physics, atomic spectral lines are of two types:* An emission line is formed when an electron makes a transition from a particular discrete energy level of an atom, to a lower energy state, emitting a photon of a particular energy and wavelength....
s.

Although it is commonly stated that all the electrons in a shell have the same energy, this is an approximation. However, the electrons in a subshell do have exactly the same level of energy, with later subshells having more energy per electron than earlier ones. This effect is great enough that the energy ranges associated with shells can overlap (see Valence shells

Electron shell

File:Periodic Table of Elements showing Electron Shells.svgAn electron shell may be crudely thought of as an orbit followed by electrons around an atom Atomic nucleus....
and Aufbau Principle

Aufbau principle

Number of electrons in each shell

Each s subshell holds at most 2 electrons

Each p subshell holds at most 6 electrons

Each d subshell holds at most 10 electrons

Each f subshell holds at most 14 electrons

Therefore, the K shell, which contains only an s subshell, can hold up to 2 electrons; the L shell, which contains an s and a p, can hold up to 2+6=8 electrons; and so forth. The general formula is that the nth shell can in principle hold up to 2n² electrons.

Although that formula gives the maximum in principle, in fact that maximum can only be achieved (by known elements) for the first four shells (K,L,M,N). In fact, no known element has more than 32 electrons in any one shell. This is because the subshells are filled according to the Aufbau principle

Aufbau principle

The Aufbau principle is used to determine the electron configuration of an atom, molecule or ion. The principle postulates a hypothetical process in which an atom is "built up" by progressively adding electrons....
. The first elements to have more than 32 electrons in one shell would belong to the g-block
G-block

Extension of the periodic table beyond the seventh period allows the inclusion of possible chemical elements with atomic number > 118 into the periodic table....
of period 8

Period 8 element

A period 8 element is one of the chemical elements in the eighth row of the periodic table . None of these elements has yet been created and it is possible that none of the elements have isotopes with stable enough nuclei to receive significant attention anytime soon....
of the periodic table

Periodic table

The periodic table of the chemical elements is a table method of displaying the chemical elements. Although precursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869....
. These elements would have some electrons in their 5g subshell and thus have more than 32 electrons in the O shell (fifth principal shell).

Valence shells

The valence shell is the outermost shell of an atom

Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
. It is usually (and misleadingly) said that the electrons in this shell make up its valence electrons, that is, the electrons that determine how the atom behaves in chemical reactions. While atoms with complete valence shells (noble gases) are the most chemically non-reactive, those with only one electron in their valence shells (alkalis) or just missing one electron from having a complete shell (halogens) are the most reactive.

However, the truth is more complicated. The electrons that determine how an atom reacts chemically are those that travel furthest from the nucleus - i.e. those with the most energy. As stated in Subshells

Electron shell

File:Periodic Table of Elements showing Electron Shells.svgAn electron shell may be crudely thought of as an orbit followed by electrons around an atom Atomic nucleus....
, electrons in the inner subshells have less energy than those in outer subshells. This effect is great enough that the 3d electrons have more energy than 4s electrons, and are therefore more important in chemical reactions, hence making them valence electrons although they are not in the so-called valence shell.

List of elements with electrons per shell

The list below gives the elements arranged by increasing atomic number and showing the number of electrons per shell. At a glance, one can see that subsets of the list show obvious patterns, in particular the seven elements (in light blue) before a noble gas

Noble gas

|}The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with a very low chemical reactivity....
(group 18, in yellow) higher than helium have the number of electrons in the valence shell in arithmetic progression. Whether this extends to Ununseptium

Ununseptium

Ununseptium is the temporary name of an undiscovered chemical element in the periodic table that has the temporary symbol Uus and the atomic number 117....
remains to be known.

Sorting the table by chemical group

Periodic table group

In chemistry, a group is a vertical column in the periodic table of the chemical elements. The name family is derived from the fact that the elements share similar characteristics and traits, just as members of any human family would....
shows additional patterns especially with respect to the last two outermost shells. (Elements 57 to 71 belongs to the lanthanides, while 89 to 103 are the actinide

Actinide

According to IUPAC nomenclature, the actinoid series encompasses the 15 chemical elements that lie between actinium and lawrencium included on the periodic table, with atomic numbers 89 - 103....
s.)

It is also seen that palladium

Palladium

Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the 2 Pallas, which in turn, was named after the epithet of the Greek mythology goddess Athena, acquired by her when she slew Athena#Pallas_Athena....
(atomic number 46) is unique being the only known element such that there are elements with smaller atomic number having more electron shells.

Z Atomic number In chemistry and physics, the atomic number is the number of protons found in the atomic nucleus of an atom. It is conventionally represented by the symbol Z....	Element Chemical element A chemical element is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its atomic nucleus. The term is also used to refer to a pure chemical Chemical substance composed of atoms with the same number of protons....	No. of electrons/shell Electron configurations of the elements (data page) << Chemical elements data references...	Group Periodic table group In chemistry, a group is a vertical column in the periodic table of the chemical elements. The name family is derived from the fact that the elements share similar characteristics and traits, just as members of any human family would....
1	Hydrogen Hydrogen Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....	1	1
2	Helium Helium Helium is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gas group in the periodic table and whose atomic number is 2....	2	18
3	Lithium Lithium Lithium is a chemical element with the symbol Li and atomic number 3. It is a soft alkali metal with a silver-white color. Under standard conditions for temperature and pressure, it is the lightest metal and the least dense solid element....	2, 1	1
4	Beryllium Beryllium Beryllium is a chemical element with the symbol Be and atomic number 4.A Bivalent element, beryllium is found naturally only combined with other elements in minerals....	2, 2	2
5	Boron Boron Boron is a chemical element with atomic number 5 and the chemical symbol B. Boron is a trivalent metalloid element which occurs abundantly in the evaporite ores borax and ulexite....	2, 3	13
6	Carbon Carbon Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....	2, 4	14
7	Nitrogen Nitrogen Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....	2, 5	15
8	Oxygen Oxygen Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...	2, 6	16
9	Fluorine Fluorine Fluorine is the chemical element with the symbol F and atomic number 9. Fluorine forms a single bond with itself in elemental form, resulting in the diatomic F2 molecule....	2, 7	17
10	Neon Neon Neon is the chemical element that has the symbol Ne and atomic number 10. Although a very common element in the universe, it is rare on Earth....	2, 8	18
11	Sodium Sodium Sodium is an element which has the symbol Na , atomic number 11, atomic mass 23 amu , and a common oxidation number +1. Sodium is a soft, silvery white, highly reactive element and is a member of the alkali metals within "group 1" ....	2, 8, 1	1
12	Magnesium Magnesium Magnesium is a chemical element with the symbol Mg, atomic number 12, atomic weight 24.3050 and common oxidation number +2.Magnesium, an alkaline earth metal, is the ninth most abundance of the chemical elements in the universe by mass....	2, 8, 2	2
13	Aluminium Aluminium Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....	2, 8, 3	13
14	Silicon Silicon Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....	2, 8, 4	14
15	Phosphorus Phosphorus Phosphorus is the chemical element that has the symbol P and atomic number 15. The name comes from the and . A Valency nonmetal of the nitrogen group, phosphorus is commonly found in inorganic phosphate minerals....	2, 8, 5	15
16	Sulfur Sulfur Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....	2, 8, 6	16
17	Chlorine Chlorine Chlorine...	2, 8, 7	17
18	Argon Argon Argon is a chemical element designated by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table ....	2, 8, 8	18
19	Potassium Potassium Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....	2, 8, 8, 1	1
20	Calcium Calcium Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal, and is the fifth most abundant element by mass in the earth's Crust ....	2, 8, 8, 2	2
21	Scandium Scandium Scandium is a chemical element with symbol Sc and atomic number 21. A silvery-white metallic transition metal, it has historically been sometimes classified as a rare earth element, together with yttrium and the lanthanides....	2, 8, 9, 2	3
22	Titanium Titanium Titanium is a chemical element with the symbol Ti and atomic number 22. Sometimes called the ?space age metal?, it has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver colour....	2, 8, 10, 2	4
23	Vanadium Vanadium Vanadium is the chemical element with the symbol V and atomic number 23. It is a soft, silvery grey, ductile transition metal. The formation of an oxide layer stabilizes the metal against oxidation....	2, 8, 11, 2	5
24	Chromium Chromium Chromium is a chemical element which has the symbol Cr and atomic number 24. It is a steely-gray, Lustre , hard metal that takes a high polish and has a high melting point....	2, 8, 13, 1	6
25	Manganese Manganese Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a Oxidation state in nature , and in many minerals....	2, 8, 13, 2	7
26	Iron Iron Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....	2, 8, 14, 2	8
27	Cobalt Cobalt Cobalt is a hard, lustrous, grey metal, a chemical element with symbol Co and atomic number 27. Although cobalt-based colors and pigments have been used since ancient times, and miners have long used the name kobold ore for some minerals, cobalt was only discovered in 1735 by Georg Brandt....	2, 8, 15, 2	9
28	Nickel Nickel Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge....	2, 8, 16, 2	10
29	Copper Copper Copper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity....	2, 8, 18, 1	11
30	Zinc Zinc Zinc is a metallic chemical element with the symbol Zn and atomic number 30. It is a first-row transition metal of the group 12 element of the periodic table....	2, 8, 18, 2	12
31	Gallium Gallium Gallium is a chemical element that has the symbol Ga and atomic number 31. Elemental gallium does not occur in nature, but as the Ga salt, in trace amounts in bauxite and zinc ores....	2, 8, 18, 3	13
32	Germanium Germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, greyish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon....	2, 8, 18, 4	14
33	Arsenic Arsenic Arsenic is a well-known chemical element that has the symbol As and atomic number 33. Arsenic was first documented by Albertus Magnus in 1250....	2, 8, 18, 5	15
34	Selenium Selenium Selenium is a chemical element with the atomic number 34, represented by the chemical symbol Se, an atomic mass of 78.96. It is a nonmetal, chemically related to sulfur and tellurium, and rarely occurs in its elemental state in nature....	2, 8, 18, 6	16
35	Bromine Bromine Bromine , , meaning "stench " ), is a chemical element with the symbol Br and atomic number 35. A halogen element, bromine is a reddish-brown Volatility liquid at Standard conditions for temperature and pressure that is intermediate in reactivity between chlorine and iodine....	2, 8, 18, 7	17
36	Krypton KRYPTON KRYPTON is a frame language computer programming language."An Essential Hybrid Reasoning System: Knowledge and Symbol Level Accounts of KRYPTON", R.J. Brachman et al, Proc IJCAI-85, 1985....	2, 8, 18, 8	18
37	Rubidium Rubidium Rubidium is a chemical element with the symbol Rb and atomic number 37. Rb is a soft, silvery-white metallic element of the alkali metal group....	2, 8, 18, 8, 1	1
38	Strontium Strontium Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically....	2, 8, 18, 8, 2	2
39	Yttrium Yttrium Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanoids and has historically been classified as a rare earth element....	2, 8, 18, 9, 2	3
40	Zirconium Zirconium Zirconium is a chemical element with the symbol Zr and atomic number 40. It is a lustrous, gray-white, strong transition metal that resembles titanium....	2, 8, 18, 10, 2	4
41	Niobium Niobium Niobium , or columbium , is a chemical element with symbol Nb and atomic number 41. A rare, soft, grey, ductile transition metal, niobium is found in the minerals pyrochlore and columbite....	2, 8, 18, 12, 1	5
42	Molybdenum Molybdenum Molybdenum , is a Group 6 element chemical element with the symbol Mo and atomic number 42. It has the List of elements by melting point melting point of any element....	2, 8, 18, 13, 1	6
43	Technetium Technetium Technetium is the lightest chemical element with no stable isotope. It is a synthetic element with the atomic number 43 and is given the symbol Tc....	2, 8, 18, 13, 2	7
44	Ruthenium Ruthenium Ruthenium is a chemical element that has the symbol Ru and atomic number 44. A rare transition metal of the platinum group of the periodic table, ruthenium is found associated with platinum ores and used as a catalyst in some platinum alloys....	2, 8, 18, 15, 1	8
45	Rhodium Rhodium Rhodium is a chemical element that is a rare, silvery-white, hard transition metal and a member of the platinum group. Rhodium is found in platinum ores and is used in alloys with platinum and as a catalyst....	2, 8, 18, 16, 1	9
46	Palladium Palladium Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the 2 Pallas, which in turn, was named after the epithet of the Greek mythology goddess Athena, acquired by her when she slew Athena#Pallas_Athena....	2, 8, 18, 18	10
47	Silver Silver Silver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal....	2, 8, 18, 18, 1	11
48	Cadmium Cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. A relatively abundant , soft, bluish-white, transition metal, cadmium is known to cause cancer and occurs with zinc ores....	2, 8, 18, 18, 2	12
49	Indium Indium Indium is a chemical element with chemical symbol In and atomic number 49. This rare, soft, malleable and easily Fusible alloy Post-transition metal is chemically similar to aluminium or gallium but more closely resembles zinc ....	2, 8, 18, 18, 3	13
50	Tin Tin Tin is a chemical element with the symbol Sn and atomic number 50. Tin is obtained chiefly from the mineral cassiterite, where it occurs as an oxide, SnO2....	2, 8, 18, 18, 4	14
51	Antimony Antimony Antimony is a chemical element with the symbol Sb and atomic number 51. A metalloid, antimony has four allotropy forms. The stable form of antimony is a blue-white metalloid....	2, 8, 18, 18, 5	15
52	Tellurium Tellurium Tellurium is a chemical element that has the symbol Te and atomic number 52. A brittle silver-white metalloid which looks like tin, tellurium is chemically related to selenium and sulfur....	2, 8, 18, 18, 6	16
53	Iodine Iodine Iodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....	2, 8, 18, 18, 7	17
54	Xenon Xenon Xenon is a chemical element represented by the chemical symbol Xe. Its atomic number is 54. A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts....	2, 8, 18, 18, 8	18
55	Caesium Caesium Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of , which makes it one of only liquid metal that are liquid at or near room temperature....	2, 8, 18, 18, 8, 1	1
56	Barium Barium Barium is a chemical element. It has the symbol Ba, and atomic number 56. Barium is a soft silvery metallic alkaline earth metal. It is never found in nature in its pure form due to its reactivity with Earth's atmosphere....	2, 8, 18, 18, 8, 2	2
57	Lanthanum Lanthanum Lanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is a lanthanoid....	2, 8, 18, 18, 9, 2
58	Cerium Cerium Cerium is a chemical element with the symbol Ce and atomic number 58....	2, 8, 18, 19, 9, 2
59	Praseodymium Praseodymium Praseodymium is a chemical element that has the symbol Pr and atomic number 59....	2, 8, 18, 21, 8, 2
60	Neodymium Neodymium Neodymium is a chemical element with the symbol Nd and atomic number 60....	2, 8, 18, 22, 8, 2
61	Promethium Promethium Promethium is a chemical element with the symbol Pm and atomic number 61. It is notable for being the only other exclusively radioactive element besides technetium which is followed by chemical elements that have stable isotopes....	2, 8, 18, 23, 8, 2
62	Samarium Samarium Samarium is a chemical element with the symbol Sm and atomic number 62....	2, 8, 18, 24, 8, 2
63	Europium Europium Europium is a chemical element with the symbol Eu and atomic number 63. It was named after the continent Europe.Characteristics ...	2, 8, 18, 25, 8, 2
64	Gadolinium Gadolinium Gadolinium is a chemical element that has the symbol Gd and atomic number 64....	2, 8, 18, 25, 9, 2
65	Terbium Terbium Terbium is a chemical element with the symbol Tb and atomic number 65....	2, 8, 18, 27, 8, 2
66	Dysprosium Dysprosium Dysprosium is a chemical element with the symbol Dy and atomic number 66. It is a rare earth element with a metallic silver luster. Dysprosium is never found in nature as a free element, though it is found in various minerals, such as xenotime....	2, 8, 18, 28, 8, 2
67	Holmium Holmium Holmium is a chemical element with the symbol Ho and atomic number 67. Part of the lanthanide series, holmium is a relatively soft and malleable silvery-white metallic element, which is stable in dry air at room temperature....	2, 8, 18, 29, 8, 2
68	Erbium Erbium Erbium is a chemical element with the symbol Er and atomic number 68. A rare, silvery, white metallic lanthanide, erbium is solid in its normal state....	2, 8, 18, 30, 8, 2
69	Thulium Thulium Thulium is a chemical element that has the symbol Tm and atomic number 69. A lanthanide element, thulium is the least abundant of the Rare earth elements....	2, 8, 18, 31, 8, 2
70	Ytterbium Ytterbium Ytterbium is a chemical element with the symbol Yb and atomic number 70. A soft silvery metallic element, ytterbium is a Rare earth element of the lanthanide series and is found in the minerals gadolinite, monazite, and xenotime....	2, 8, 18, 32, 8, 2
71	Lutetium Lutetium Lutetium is a chemical element with the symbol Lu and atomic number 71. A silvery-white rare metal, lutetium is the heaviest member of the rare-earth group....	2, 8, 18, 32, 9, 2	3
72	Hafnium Hafnium Hafnium is a chemical element with the element symbol Hf and atomic number 72. A lustre , silvery gray, tetravalence, transition metal, hafnium chemically resembles zirconium and is found in zirconium minerals....	2, 8, 18, 32, 10, 2	4
73	Tantalum Tantalum Tantalum is a chemical element with the symbol Ta and atomic number 73. A rare, hard, blue-grey, lustre transition metal, tantalum is highly corrosion-resistant and occurs naturally in the mineral tantalite, always together with the chemically similar niobium....	2, 8, 18, 32, 11, 2	5
74	Tungsten Tungsten Tungsten , also known as wolfram , is a chemical element that has the symbol W and atomic number 74.A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite....	2, 8, 18, 32, 12, 2	6
75	Rhenium Rhenium Rhenium is a chemical element with the symbol Re and atomic number 75. A rare silvery-white, heavy, polyvalent transition metal, rhenium resembles manganese chemically, and is used in some alloys....	2, 8, 18, 32, 13, 2	7
76	Osmium Osmium Osmium is a chemical element that has the symbol Os and atomic number 76. Osmium is a hard, brittle, blue-gray or blue-black transition metal in the platinum family, and is the densest natural element....	2, 8, 18, 32, 14, 2	8
77	Iridium Iridium Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum group, iridium is the second densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 ?C....	2, 8, 18, 32, 15, 2	9
78	Platinum Platinum Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements....	2, 8, 18, 32, 17, 1	10
79	Gold Gold Gold is a chemical element with the symbol Au and atomic number 79. It is a highly sought-after precious metal, having been used as money, as a store of value, in jewelry, in sculpture, and for ornamentation since the beginning of recorded history....	2, 8, 18, 32, 18, 1	11
80	Mercury Mercury (element) Mercury , also called quicksilver or hydrargyrum , is a chemical element with the symbol Hg and atomic number 80. A heavy, silvery d-block metal, mercury is one of six elements that are liquid at or near room temperature and pressure....	2, 8, 18, 32, 18, 2	12
81	Thallium Thallium Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray malleable poor metal resembles tin but discolors when exposed to air....	2, 8, 18, 32, 18, 3	13
82	Lead Lead Lead is a main-group Chemical element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metal ....	2, 8, 18, 32, 18, 4	14
83	Bismuth Bismuth Bismuth is a chemical element that has the symbol Bi and atomic number 83. This heavy, brittle, white crystalline trivalent poor metal has a pink tinge and chemically resembles arsenic and antimony....	2, 8, 18, 32, 18, 5	15
84	Polonium Polonium Polonium is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie Curie and Pierre Curie. A rare and highly radioactive metalloid, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores....	2, 8, 18, 32, 18, 6	16
85	Astatine Astatine Astatine is a radioactive chemical element with the symbol At and atomic number 85. It is the heaviest of the discovered halogens. Although astatine is produced by Radioactive decay Decay chain in nature, due to its short half life it is found only in minute amounts....	2, 8, 18, 32, 18, 7	17
86	Radon Radon Radon is a chemical element with symbol Rn and atomic number 86. Radon is a colorless, odorless, tasteless, naturally occurring, radioactive noble gas that is formed from the decay of radium....	2, 8, 18, 32, 18, 8	18
87	Francium Francium Francium , formerly known as Mendeleev's predicted elements-caesium and actinium K, is a chemical element that has the symbol Fr and atomic number 87....	2, 8, 18, 32, 18, 8, 1	1
88	Radium Radium Radium is a radioactive chemical element which has the symbol Ra and atomic number 88. Its appearance is almost pure white, but it readily oxidizes on exposure to air, turning black....	2, 8, 18, 32, 18, 8, 2	2
89	Actinium Actinium Actinium is a radioactive chemical element with the symbol Ac and atomic number 89, which was discovered in 1899. It was the first Primordial element to be isolated, although polonium, radium and radon were observed before, but not isolated until 1902....	2, 8, 18, 32, 18, 9, 2
90	Thorium Thorium Thorium is a chemical element with the symbol Th and atomic number 90. As a naturally occurring, slightly radioactive metal, it has been considered as an alternative nuclear fuel to uranium....	2, 8, 18, 32, 18, 10, 2
91	Protactinium Protactinium Protactinium is a chemical element with the symbol Pa and atomic number 91. Its longest-lived isotope has a half-life of 32,760 years....	2, 8, 18, 32, 20, 9, 2
92	Uranium Uranium Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....	2, 8, 18, 32, 21, 9, 2
93	Neptunium Neptunium Neptunium is a chemical element with the symbol Np and atomic number 93. A radioactivity metallic element, neptunium is the first transuranic element and belongs to the actinide series....	2, 8, 18, 32, 22, 9, 2
94	Plutonium Plutonium Plutonium is a rare transuranic radioactive chemical element. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when plutonium oxide....	2, 8, 18, 32, 24, 8, 2
95	Americium Americium Americium is a synthetic element that has the symbol Am and atomic number 95. A radioactive decay metallic element, americium is an actinide that was obtained in 1944 by Glenn T....	2, 8, 18, 32, 25, 8, 2
96	Curium Curium Curium is a synthetic element with the symbol Cm and atomic number 96. A Radioactive decay metallic transuranic element of the actinide series, curium is produced by bombarding plutonium with alpha particles and was named for Maria Sklodowska-Curie and her husband Pierre Curie....	2, 8, 18, 32, 25, 9, 2
97	Berkelium Berkelium Berkelium is a synthetic element with the symbol Bk and atomic number 97. A radioactive metallic element in the actinide series, berkelium was first synthesized by bombarding americium with alpha particles and was named after the University of California, Berkeley....	2, 8, 18, 32, 27, 8, 2
98	Californium Californium Californium is a metallic chemical element with the symbol Cf and atomic number 98. A Radioactive decay transuranic element, californium is used in starting nuclear reactors, optimizing coal-fired power plants and cement production facilities , medical treatment of cancer, and oil exploration via down hole well logging....	2, 8, 18, 32, 28, 8, 2
99	Einsteinium Einsteinium Einsteinium is a metallic synthetic element. On the periodic table, it is represented by the symbol Es and atomic number 99. It is the seventh transuranic element, and seventh in the series of actinoids....	2, 8, 18, 32, 29, 8, 2
100	Fermium Fermium Fermium is a synthetic element with the symbol Fm and atomic number 100. A highly radioactive metallic transuranic element of the actinide series, fermium is made by bombarding plutonium with neutrons and is named after nuclear physicist Enrico Fermi....	2, 8, 18, 32, 30, 8, 2
101	Mendelevium Mendelevium Mendelevium is a synthetic element with the symbol Md and the atomic number 101. A metallic radioactive transuranic element of the actinides, mendelevium is synthesized by bombarding einsteinium with alpha particles and was named after Dmitri Mendeleev, who was responsible for the Periodic Table....	2, 8, 18, 32, 31, 8, 2
102	Nobelium Nobelium Nobelium is a synthetic element with the symbol No and atomic number 102. It was first correctly identified in 1956 by scientists at the Flerov Laboratory of Nuclear Reactions in Dubna, Russia....	2, 8, 18, 32, 32, 8, 2
103	Lawrencium Lawrencium Lawrencium is a radioactive synthetic element with the symbol Lr and atomic number 103.Its most stable known isotope is 262Lr, with a half-life of approximately 3.6 hours....	2, 8, 18, 32, 32, 8, 3	3
104	Rutherfordium Rutherfordium Rutherfordium is a chemical element in the periodic table that has the symbol Rf and atomic number 104.This is a radioactive synthetic element whose most stable known isotope is 267Rf with a half-life of approximately 1.3 hours....	2, 8, 18, 32, 32, 10, 2	4
105	Dubnium Dubnium Dubnium is a chemical element in the periodic table that has the symbol Db and atomic number 105.This is a radioactive synthetic element whose most stable isotope is 268Db with a half life of 28 hours....	2, 8, 18, 32, 32, 11, 2	5
106	Seaborgium Seaborgium Seaborgium is a chemical element in the periodic table that has the symbol Sg and atomic number 106.Seaborgium is a synthetic element whose most stable isotope 271Sg has a half-life of 1.9 minutes....	2, 8, 18, 32, 32, 12, 2	6
107	Bohrium Bohrium Bohrium is a chemical element in the periodic table that has the symbol Bh and atomic number 107.It is a synthetic element whose most stable isotope, 270Bh, has a half-life of 61 seconds....	2, 8, 18, 32, 32, 13, 2	7
108	Hassium Hassium Hassium is a synthetic element in the periodic table that has the symbol Hs and atomic number 108. Hassium oxidizes similarly to osmium above it, to a hassium tetroxide with a lower Volatility than osmium tetroxide....	2, 8, 18, 32, 32, 14, 2	8
109	Meitnerium Meitnerium Meitnerium is a chemical element in the periodic table that has the symbol Mt and atomic number 109.Mt is a synthetic element whose most stable isotope, Mt-278, has a predicted half-life of a half-hour....	2, 8, 18, 32, 32, 15, 2	9
110	Darmstadtium Darmstadtium Darmstadtium , formerly known as Ununnilium, is a chemical element with the symbol Ds and atomic number 110.This synthetic element is one of the so-called super-heavy atoms....	2, 8, 18, 32, 32, 17, 1	10
111	Roentgenium Roentgenium Roentgenium is a chemical element in the periodic table that has the symbol Rg and atomic number 111.It is a synthetic element whose most stable known isotope has a mass of 283 atomic mass unit and an estimated half-life of ten minutes....	2, 8, 18, 32, 32, 18, 1	11
112	Ununbium Ununbium Ununbium is a temporary IUPAC systematic element name for a chemical element in the periodic table that has the systematic element name symbol Uub and the atomic number 112....	2, 8, 18, 32, 32, 18, 2	12
113	Ununtrium Ununtrium Ununtrium is the temporary name of a synthetic element in the periodic table that has the temporary symbol Uut and has the atomic number 113....	2, 8, 18, 32, 32, 18, 3	13
114	Ununquadium Ununquadium Ununquadium is the temporary name of a radioactivity chemical element in the periodic table that has the temporary symbol Uuq and has the atomic number 114....	2, 8, 18, 32, 32, 18, 4	14
115	Ununpentium Ununpentium Ununpentium is the temporary name of a synthetic element superheavy element in the periodic table that has the temporary symbol Uup and has the atomic number 115....	2, 8, 18, 32, 32, 18, 5	15
116	Ununhexium Ununhexium Ununhexium is the temporary name of a synthetic element superheavy element in the periodic table that has the temporary symbol Uuh and has the atomic number 116....	2, 8, 18, 32, 32, 18, 6	16
117	Ununseptium Ununseptium Ununseptium is the temporary name of an undiscovered chemical element in the periodic table that has the temporary symbol Uus and the atomic number 117....	2, 8, 18, 32, 32, 18, 7	17
118	Ununoctium Ununoctium Ununoctium , also known as Mendeleev's predicted elements or element 118, is the temporary International Union of Pure and Applied Chemistry systematic element name for the transactinide element having the atomic number 118 and temporary chemical symbol Uuo....	2, 8, 18, 32, 32, 18, 8	18

Electron shell

History

Shells

Subshells

Number of electrons in each shell

Valence shells

List of elements with electrons per shell

See also