Valence Electrons

Valence Electrons Classification Of Elements And Periodicity Explanation

Electrons present in the outer most shell are called as Valence Electrons. They determine the chemical properties of the element.

Valence electrons of charged atoms

We know that electrons are negatively charged. When an atom is negatively charged, it means that there are more atoms in the outermost shell than the normal valance number. Similarly, a positive charged atom will have less number of electrons in the outermost orbit than the normal valance electrons

No. of valence electrons   =  Valence of Group – Charge

For example, Calcium has two valence electrons. Ca++ has zero valence electrons because 2+ charge indicates that two electrons would be missing in the outermost orbit.


Valency is the number of electrons an atom needs to gain or release in order to attain fullest energy level. When an atom contains below four electrons in its outermost shell, the valency is equal to the number of valence electrons and it is said to have a positive valency(donates its free electrons to another atom with negative valency). When the number of electrons in atom is above 4, it has a negative valency(accepts free electrons from another atom with positive valency).  Valency of such an element is determined by subtracting the number of valence electrons from 8.

Important Points to Remember:

  1. Valence Electrons remain same within the elements of the group and increases for elements across a period.
  2. The group number of an element is equal to the number of valence electrons.
  3. It determines the chemical properties of the element.
  4. It forms bond with other atoms and elements.
  5. The number of bonds can be determined by the number of valence electrons in the element.

Related Concepts:

Element, Orbitals, Electronic Configuration

Related Questions:

  1. The correct set of four quantum numbers for the valence electron
  2. If N is Avagadro number, then number of valence electrons in 4.2g of nitride
Topics: Classification of Elements and Periodicity (10)
Subject: Chemistry (2785)

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