Abegg's rule

In chemistry

Chemistry

Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

, Abegg’s rule states that the difference between the maximum positive and negative valence

Valence (chemistry)

In chemistry, valence, also known as valency or valence number, is a measure of the number of bonds formed by an atom of a given element. "Valence" can be defined as the number of valence bonds...

 of an element

Chemical element

A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

 is frequently eight. The rule used a historic meaning of valence which resembles the modern concept of oxidation state

Oxidation state

In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...

 in which an atom is an electron donor or receiver. Abegg’s rule is sometimes referred to as "Abegg’s law of valence and countervalence".

In general, for a given chemical element (as sulfur

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

) Abegg’s rule states that the sum of the absolute value of its negative valence (such as −2 for sulfur in H₂S) and its positive valence of maximum value (as +6 for sulfur in H₂SO₄) is often equal to 8.

History

The concept was formulated in 1904 by German chemist Richard Abegg

Richard Abegg

Richard Wilhelm Heinrich Abegg was a German chemist and pioneer of valence theory. He proposed that the difference of the maximum positive and negative valence of an element tends to be eight. This has come to be called Abegg's rule...

. Gilbert N. Lewis

Gilbert N. Lewis

Gilbert Newton Lewis was an American physical chemist known for the discovery of the covalent bond , his purification of heavy water, his reformulation of chemical thermodynamics in a mathematically rigorous manner accessible to ordinary chemists, his theory of Lewis acids and...

 was one of the first to refer to the concept as "Abegg’s rule" when he used it as a basis of argument in Gilbert N. Lewis

Gilbert N. Lewis

Gilbert Newton Lewis was an American physical chemist known for the discovery of the covalent bond , his purification of heavy water, his reformulation of chemical thermodynamics in a mathematically rigorous manner accessible to ordinary chemists, his theory of Lewis acids and...

’ 1916 famous article "The Atom and the Molecule", to develop his cubical atom

Cubical atom

The cubical atom was an early atomic model in which electrons were positioned at the eight corners of a cube in a non-polar atom or molecule. This theory was developed in 1902 by Gilbert N. Lewis and published in 1916 in the famous article "The Atom and the Molecule" and used to account for the...

 theory, which developed into the octet rule

Octet rule

The octet rule is a chemical rule of thumb that states that atoms of low The octet rule is a chemical rule of thumb that states that atoms of low The octet rule is a chemical rule of thumb that states that atoms of low (The octet rule is a chemical rule of thumb that states that atoms of low (...

. "The Atom and the Molecule" article helped inspire Linus Pauling

Linus Pauling

Linus Carl Pauling was an American chemist, biochemist, peace activist, author, and educator. He was one of the most influential chemists in history and ranks among the most important scientists of the 20th century...

to write the famous 1938 textbook The Nature of the Chemical Bond.

External links

• Abegg’s rule - Omnificent English Dictionary In Limerick Form
• Nuclear Atom - contains and excerpt of Abegg's contributions.