How does atomic radius change from left to right across a period in the periodic table?

a. it first decreases, then increases.
b. it tends to decrease.
c. it first increases, then decreases.
d. it tends to increase.

Option (b) is the correct answer.

Explanation:

When we move from left to right across a period in a periodic table then there will occur a decrease in size of the atoms because electrons are added to the same shell.

As a result, nucleus tends to pull the electrons towards itself due to which shrinkage in the size of atoms tends to occur.

Thus, we can conclude that atomic radius tends to decrease from left to right across a period in the periodic table.

the electronic configuration of an atom with eight electrons is 1s²2s²2p⁴. the orbital diagrams are shown in the figure.

as per the hunds rule:

1. electrons tend to avoid being in the same orbital as per as practicable.

2. electrons in different orbitals of the same energy will have their spin parallel.

this can be illustrated from the multiplicity of the orbitals of the atom. as there are four electrons in the p orbital and p orbital has 3 sub-shells. the electrons can be fed in different ways as shown in the figure but the correct orbital diagram will be as per the hunds rule.