Question

An atom with $3$ protons and $4$ neutrons will have a valency of:

• A. 3
• B. 7
• C. 1
• D. 4

Answer 1

The correct option is C

1

Given:

Number of protons$=3$

Number of neutrons$=4$

Formula used:

Number of electrons in a neutral atom$=$Number of protons

Calculate the number of electrons in the atom:

In a neutral atom,

Number of electrons$=$Number of protons

Number of electrons$=3$

Write the electronic configuration of the atom:

1. The atom has $3$ electrons.
2. Thus, the $\mathrm{K}$ shell holds $2$ electrons and the $\mathrm{L}$ shell holds remaining $1$ electron.
3. Thus, the electronic configuration of the atom is $(2,1)$.

Determine the valency of the atom:

1. The combining capacity of the atom of an element with the atoms of other elements in order to acquire eight electrons (or two electrons in Helium) in its outermost shell is known as valency.
2. The electronic configuration of the atom is $(2,1)$.
3. In order to acquire $2$ electrons in the outermost shell i.e. to complete the duplet, the atom loses $1$ electron.
4. Thus, the valency of the atom is $1$.

Thus, Option (C) is the correct option.