Question

a) How do you calculate the valency of an element from its electronic configuration?
b) What is the valency of magnesium with atomic number $12$ and sulphur with atomic number $16$?
c) How does the valency vary in a period going from left to right?
d) How does the valency vary in going down a group?

Answer 1

The chemical elements consist of electrons in its shells. The electrons in the shells were named as two types. Valence electrons and core electrons. The valency electrons will be loosely held. The chemical elements try to attain the nearest noble or inert gas configuration by gaining or losing electrons.

Complete answer:
The chemical elements consist of electrons in their shells and try to attain the nearest noble or inert gas configuration by gaining or losing electrons.
a) The number of electrons gained or lost to attain nearest noble or inert gas configuration can be represented as valency. When element gains it can be represented as negative and when element loses electrons it can be represented as positive.
b) Magnesium is an element with atomic number $12$ and the valency is $+ 2$, sulphur with atomic number $16$ and the valency is $- 2$.
c)the valency in the periods increases from left to right.
d)The valency will be constant in going from down a group.

Note:
Metals are placed at the extreme left side of the periodic table. They will easily lose electrons and have positive valency as they will lose electrons and nonmetals placed at the right side of the periodic table and have negative valency numbers as they try to gain electrons.