Question

How does the following properties vary in the third period:

1. Atomic size
2. Metallic character
3. Ionisation energy.

Answer 1

1. Atomic size is the distance between the centre of nucleus and the outermost electron in the outer shell. Atomic radius decreases because the electrons enters in the 3^rd orbit the electrons entering the same orbit have less shielding power but nuclear charge increases.
2. From sodium to argon in the third period metallic character decreases, as we move from left to right because non-metallic character increases.
3. Ionisation energy increases across the third period because the nuclear charge increases but the shielding of the outer electrons remain the same.