Question

define the valency by taking examples of silicon and oxygen

Answer 1

Valency-Number of protons present in the outermost shell of an atom is known as Valency or The combining power of a element with a atom is also known as Valency.

Taking oxygen as Example-

1.Atomic number of Oxygen is8.
2.Electronic configuration-K=2,L=6.
3.According to the electronic configuration the valency is 6 but it is easy for oxygen to gain 2 protons instead of loosing 6 protons.So, The valency of oxygen is 2.

Taking silicon as example-

1.Atomic number of silicon is 14.
2.Electronic configuration-K=2,L=8,m=4.
3.According to the electronic configuration the valency is +4 or -4 because silicon can either gain 4 electrons or loose 4 electrons because it is a noble gas.

Answer 2

Valency is defined as the number of electrons gained or lost or shared to complete the octet in valence shell

Now,silicon:
Its electronic configuration is 2, 8, 4
4 electrons are shared to complete the octet so its valency is 4

Next,oxygen:
Its electronic configuration is 2, 6
It will gain 2 electrons are needed to complete the octet.So its valency is 2.

Hope it helps you.............