Question

Define valency by taking examples of silicon and oxygen

Answer 1

The valency of an element is the combining capacity of that element. The valency of an element is determined by the number of valence electrons present in the atom of that element.

→ Valency of Silicon: It has electronic configuration: 2,8,4

Thus, the valency of silicon is 4 as these electrons can be shared with others to complete octet.

→ Valency of Oxygen: It has electronic configuration: 2,6

Thus, the valency of oxygen is 2 as it will gain 2 electrons to complete its octet.

Answer 2

The valency of an element is the combining capacity of that element. The valency of an element is determined by the number of valence electrons present in the atom of that element. If the number of valence electrons of the atom of an element is less than or equal to four, then the valency of that element is equal to the number of valence electrons. For example, the atom of silicon has four valence electrons. 

Thus, the valency of silicon is four. On the other hand, if the number of valence electrons of the atom of an element is greater than four, then the valency of that element is obtained by subtracting the number of valence electrons from eight. For example, the atom of oxygen has six valence electrons. Thus, the valency of oxygen is (8 − 6) i.e., two.