Question

Explain the difference between valence shell electrons and valency with help of an example ?

Answer 1

The combining capacity of an atom is called its valency. Actually it can be defined as the number of electrons that an atom may lose (or) gain during a chemical reaction (or) the number of electrons shared. [1 Mark]

The number of electrons in outermost shell (or) valency shell of an atom are called valence electrons. [1 Mark]

Example:
In water molecule $H_{2}O$ (H - O – H) the valency of hydrogen is '1' (as it combines with one oxygen atom ) and valence electrons in hydrogen = 1.
On the other hand valency of oxygen is '2' (as it combines with two Hydrogen atoms) but valence electrons in oxygen = 6.
[1 Mark]