Question

Assertion: Valency of an element is its combining capacity with the atoms of other elements.
Reason: Elements take part in chemical combination to acquire the electronic configuration of the
nearest noble gas element.
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Answer 1

Answer:

both A and R are correct and R is correct explanation of A

Answer 2

Answer:

The number of hydrogen atoms which combine with one atom of the element is called the combining number or valency of the element.

For example –  

One hydrogen atom combines with one chlorine atom to form hydrogen chloride (HCl) and thus the valency of chlorine atom is one. Elements with valency of one are called as univalent.

Two hydrogen atoms combine with one oxygen atom to form water (H2O) and thus the valency of oxygen atom is two. Elements with valency of two are called as divalent.

Three hydrogen atoms combine with one nitrogen atom to form ammonia (NH3) and thus the valency of nitrogen atom is three. Elements with valency of three are called as trivalent.

Four hydrogen atoms combine with one carbon atom to form methane (CH4) and thus the valency of carbon atom is four. Elements with valency of four are called as tetravalent.

Some elements (noble gases or inert gases e.g. helium, neon, argon etc.) do not generally combine with other elements and thus they have zero valency. Such elements are known as zerovalent.