Question

How do we calculate the valency of an element from its eletronic configuration?

Answer 1

The valency of an element is determined by the number of valence electrons present in the outermost shell of its atom. The number of electrons lost or gained (or shared) by one atom of anelement to achieve the nearest inert gaselectron configuration, gives us thevalency of the element.

Answer 2

Explanation:

Electronic configuration means arranging electrons in shells , subshells and orbitals

For example Magnesium :

Atomic number 12

electronic configuration: 1s2 2s2  2p6 3s2

valence electrons : 2

hence to attain stability magnesium will lose 2 electrons . Hence valency is 2.

so based on valence electrons valency is calculated.

b] Valency in a period:

As we move in a period from left to right in each short period of  a periodic table valency increases from 1 to 4 and then decreases to zero.

for example:

Third period : Na Mg  Al    Si    P   S   Cl Ar 

                       1    2     3     4    3    2    1  0

so elements in the same period have different valencies.