State the factors which affect the atomic size of elements in a periodic table. In period 2 from left to right, state which element has the largest atomic size and which has the smallest, giving reasons.

Factors affecting the atomic size are:

1. Number of shells — An increase in the number of shells increases the size of an atom because the distance between the outermost shell and the nucleus increases.
2. Nuclear charge — An increase in nuclear charge decreases the size of the atom because the electrons are then attracted towards the nucleus with a greater force thereby bringing the outermost shell closer to the nucleus.

In period 2 from left to right, Li has the largest atomic size and F has the smallest atomic size. This is so because the nuclear charge i.e., the atomic number increases from left to right in the same period, thereby bringing the outermost shell closer to the nucleus.