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Alkali metal
 
 
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The alkali metals are a series of chemical 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....
s comprising Group 1
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....
 (IUPAC
International Union of Pure and Applied Chemistry

The International Union of Pure and Applied Chemistry is a non-governmental organization established in 1919 for the advancing of chemistry. Its members are national chemistry societies....
 style) 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....
: 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....
 (Li), 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" ....
 (Na), 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....
 (K), 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....
 (Rb), 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....
 (Cs), and 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....
 (Fr). (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....
, although nominally also a member of Group 1, very rarely exhibits behavior comparable to the alkali metals). The alkali metals provide one of the best examples of group trends in properties in the periodic table, with well characterized homologous behavior down the group.

The alkali metals are all highly reactive and are never found in elemental form in nature.






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The alkali metals are a series of chemical 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....
s comprising Group 1
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....
 (IUPAC
International Union of Pure and Applied Chemistry

The International Union of Pure and Applied Chemistry is a non-governmental organization established in 1919 for the advancing of chemistry. Its members are national chemistry societies....
 style) 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....
: 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....
 (Li), 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" ....
 (Na), 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....
 (K), 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....
 (Rb), 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....
 (Cs), and 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....
 (Fr). (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....
, although nominally also a member of Group 1, very rarely exhibits behavior comparable to the alkali metals). The alkali metals provide one of the best examples of group trends in properties in the periodic table, with well characterized homologous behavior down the group.

The alkali metals are all highly reactive and are never found in elemental form in nature. As a result, in the laboratory they are stored under mineral oil
Mineral oil

Mineral oil or liquid petroleumis a by-product in the distillation of petroleum to produce gasoline and other petroleum based products from crude oil....
. They also tarnish easily and have low melting points and densities. Potassium and rubidium possess a weak radioactive characteristic (harmless) due to the presence of long duration radioactive isotopes.

The alkali metals are silver-colored (caesium has a golden tinge), soft, low-density
Density

The density of a material is defined as its mass per unit volume. The symbol of density is ....
 metal
Metal

In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions , and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....
s, which react readily with halogen
Halogen

|}The halogens or halogen elements are a chemical series of nonmetal chemical element from Periodic table group International Union of Pure and Applied Chemistry of the periodic table, comprising fluorine, F; chlorine, Cl; bromine, Br; iodine, I; and astatine, At....
s to form ionic salts, and with water
Water (molecule)

File:Blue-water-pool.jpgWater is the most abundant molecule on Earth's surface, constituting about 70% of the Earth's surface in liquid, solid, and gaseous states....
 to form strongly alkali
Alkali

In chemistry, an alkali is a Base , Ionic compound salt of an alkali metal or alkaline earth metal Chemical element. Alkalis are best known for being Base s that dissolve in water....
ne (basic)
Base (chemistry)

In chemistry, a base is most commonly thought of as an aqueous substance that can accept protons. A base is also often referred to as an alkali if OH- ions are involved....
 hydroxide
Hydroxide

In chemistry, hydroxide is the name for the Diatomic molecule anion OH-, consisting of oxygen and hydrogen atoms, usually derived from the Dissociation of a base ....
s. These elements all have one electron
Electron

The electron is a subatomic particle that carries a negative electric charge. It has elementary particle and is believed to be a point particle....
 in their outermost shell, so the energetically preferred state of achieving a filled electron shell
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....
 is to lose one electron to form a singly charged
Electric charge

Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields....
 positive ion
Ion

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. According to the Bohr_model this will be from or in the outer shield 'n'....
, i.e. cation.

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....
, with a solitary electron, is usually placed at the top of Group 1 of the periodic table, but it is not considered an alkali metal; rather it exists naturally as a diatomic gas
Gas

In physics, a gas is a state of matter, consisting of a collection of particles without a definite shape or volume that are in more or less random motion....
. Removal of its single electron requires considerably more energy than removal of the outer electron for the alkali metals. As in the halogen
Halogen

|}The halogens or halogen elements are a chemical series of nonmetal chemical element from Periodic table group International Union of Pure and Applied Chemistry of the periodic table, comprising fluorine, F; chlorine, Cl; bromine, Br; iodine, I; and astatine, At....
s, only one additional electron is required to fill in the outermost shell of the hydrogen atom, so hydrogen can in some circumstances behave like a halogen, forming the negative hydride
Hydride

Hydride is the name given to the Electric charge ion of hydrogen, H-. Although this ion does not exist except in extraordinary conditions, the term hydride is widely applied to describe Chemical compound of hydrogen with other chemical element, particularly those of Periodic table group 1–16....
 ion. Binary compound
Binary compound

A binary compound is a chemical compound that contains exactly two different chemical element. Examples are NaCl , NaF , and MgO ....
s of hydride with the alkali metals and some transition metal
Transition metal

In chemistry, the term transition metal has two possible meanings:*It commonly refers to any element in the d-block of the periodic table, including the group 12 element elements zinc, cadmium and Mercury ....
s have been prepared. Under extremely high pressure
Pressure

Pressure is the force per unit area applied to an object in a direction surface normal to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
, such as is found at the core of Jupiter
Jupiter

Jupiter is the fifth planet from the Sun and the Solar system by size planet within the Solar System. It is two and a half times as massive as all of the other planets in our Solar System combined....
, hydrogen does become metallic and behaves like an alkali metal; see metallic hydrogen
Metallic hydrogen

Metallic hydrogen results when hydrogen is sufficiently compressed and undergoes a Phases of matter change; it is an example of degenerate matter....
.

Alkali metals have the lowest ionization potentials in their respective periods, as removing the single electron from the outermost shell gives them the stable inert gas configuration. Their second ionization potentials are very high, as removing an electron from a species having a noble gas configuration is very difficult.

Alkali metals are famous for their vigorous reactions with water, and these reactions become increasingly violent as one moves down the group. The reaction with water is as follows:

Alkali metal + water ? Alkali metal hydroxide + hydrogen gas

With 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....
 as an example:

2K (s) + 2H2O (l) ? 2KOH (aq) + H2 (g)


Trends


Like other groups, the members of this family show patterns in its electron configuration, especially the outermost shells resulting in trends in chemical behavior:

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
Element

The name element may refer to:In chemistry, electronics or the geosciences:* Chemical element, an atomic structure* Electrical element...
 		 No. of electrons/shell
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....
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
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
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
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
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
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
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


The alkali metals show a number of trends when moving down the group - for instance,decreasing electronegativity, increasing reactivity, and decreasing melting and boiling point. Density generally increases, with the notable exception of potassium being less dense than sodium, and the possible exception of francium being less dense than caesium.



























































Alkali metal Standard Atomic Weight (u) Melting Point (K
Kelvin

The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero ....
)		 Boiling Point (K
Kelvin

The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero ....
)		 Density (g
Gram

The gram , ; symbol g, is a Physical unit of mass.Originally defined as "the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre, and at the temperature of melting ice" , a gram is now defined as one one-thousandth of the SI base unit, the kilogram, or Scientific notation kg, which itself is...
·cm-3)		 Electronegativity (Pauling)
Lithium 6.941 453 1615 0.534 0.98
Sodium 22.990 370 1156 0.968 0.93
Potassium 39.098 336 1032 0.89 0.82
Rubidium 85.468 312 961 1.532 0.82
Caesium 132.905 301 944 1.93 0.79
Francium (223) 295 950 1.87 0.70


Reference material





  • "Physics Update." Physics Today June 1996: 9.


  • "Visual Elements: Group 1 - The Alkali Metals." Visual Elements. Royal Society of Chemistry. .


See also

  • 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....
  • 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" ....
  • 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....
  • 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....
  • 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....
  • 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....


External links

  • A simple look at alkali metals
  • An in-depth look at alkali metals


Explanation of above periodic table slice:
Alkali metals Atomic numbers in are solids Solid borders indicate primordial elements (older than the Earth
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
)		 Dashed borders indicate natural radioactive element
Radioactive decay

Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, called the daughter nuclide....
s with no isotopes older than the Earth