Question

The best reason to account for the general
tendency of atomic diameters to decrease as the
atomic numbers increase within a period of the
periodic table is the fact that​

Answer 1

Answer:

in group atomic radius increase

in periods atomic radius decreases

Answer 2

Since a nuclear charge along the period increases the attraction of electrons towards the nucleus increases resulting in decrease of size atom.

Along the group the no. of shells increases and it's nuclear charge increases but the effect of no. of shell is quite larger then nuclear charge and hence size increases.

Hope it helps!