Answer to Question #162478 in Organic Chemistry for Stormy

Question

Explain why an atom in the 4th period is larger than the 3rd period.

Answer 1

An atom in the third period has three electronic shells which are more closer to the nucleus than the four electronic shells in an atom in fourth period. The force of attraction between the positive nuclear charge and the electron cloud in the atom in period three is thus greater, this makes the electron cloud be pulled more inwards towards the centered nucleus, and thereby lowering the radius of the period three atom. On the other hand, the atom in fourth period has electron clouds farther from the nucleus and hence lower attractive force from the nuclear charge. It therefore maintains a larger atomic size.