Question

An element X has a mass number 4 and an atomic number 2. Write the valency of this element?

Answer 1

Given, Mass number of element $\mathrm{X}=4$
Given, Atomic number of element $\mathrm{X}=2$

Step-1: Find the total number of electrons:

As Atomic number= Number of protons= number of electrons in an atom

Therefore, the number of electrons$=2$

Step-2: Write the electronic configuration:

• The electronic configuration of the element$=2$ and the number of electrons present in the outermost shell$=2$

Step-3: Find out the valency:

Valency: Valency is the combining capacity of an element.

• As the duplet of electrons is complete for the given element, it is stable.
• Additionally, due to zero valency, the atoms of noble gases with fully filled valence shells are inert and do not take part in chemical reactions.

As the maximum number of electrons that can be filled in the first or K shell is 2 and two electrons are present in it, therefore the valency of the given element is zero.