What is a Valence Electron | Valence Electron Definition

What is a Valence Electron

In chemistry, valence electrons are called electrons located on the outer, or valence, shell of an atom. Valence electrons determine the behavior of a chemical element in chemical reactions. The fewer valence electrons an element has, the more easily it gives up these electrons in reactions with other elements (displaying the properties of a reducing agent). 


Conversely, the more valence electrons an atom of a chemical element has, the easier it is to gain electrons (displaying the properties of an oxidizing agent) in chemical reactions, all other things being equal. Fully filled outer electron shells contain inert gases that exhibit minimal chemical activity. The frequency of filling the outer electron shell with electrons determines the periodic changes in the chemical properties of the elements in the periodic table. 


Valence Electron Examples 

  • The ground state configuration of magnesium electrons is 1s 22s 2 p 6 3s 2, the valence electrons would be 3s electrons, since 3 is the highest principal quantum number. 
  • The ground state configuration of bromine electrons is 1s 22s 2 p 6 3s 2 p 6 q 10 4s 2 p 5, the valence electrons will be 4s and 4p electrons. 


Valence Electron Definition

Electron valency is the electron that is most likely to be involved in a chemical reaction. They are usually the electrons with the highest principal quantum number, n. Another way to think of valence electrons is that they are the outermost electrons in an atom, which is why they are most susceptible to participating in chemical bonding or ionization. The easiest way to identify valence electrons is to look for the largest number in an atom’s electron configuration (the principal quantum number). 

It is worth noting the IUPAC definitions of valency for the single highest valency value displayed by an atom of an element. However, in practical use, the major groups of elements of the periodic table can exhibit any valency from 1 to 7 (with 8 being the perfect octave). 

Most of the elements have preferred valence electron values. Alkali metals, for example, almost always exhibit valency 1. Alkaline earth metals exhibit valency 2. The valency of halogens is usually 1, but can sometimes exhibit a valency of 7. Transition metals can exhibit a range of valency values, as the highest electron energy is only a partially filled subshell. These atoms become more stable by emptying the shell, filling it halfway or filling it completely.


[What is a Valence Electron | Valence Electron Definition]


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