Describe the general trends in the following properties of the elements in Groups-13
Atomic size

Explanation

Atomic size : In elements of group 13, as the atomic number increases, new electron shell gets added and so the distance between the nucleus and outermost orbital having electron increases.
Anyhow, there is exception in atomic radius of Al and Ga, the atomic radius of Al (143 pm) is more than atomic radius of Ga (135 pm) because there is no d-orbital in electronic configuration of Al while there is d-orbital in electronic configuration of Ga.
As the d-orbitals are large in size, hence the magnitude of screening effect decreases with nucleus by electrons present in them.
Now the nuclear charge of Gallium is high, as a result the attraction towards the nucleus by outermost electron increases. Hence, atomic radius of Ga is less than that of Al.