The elements of the second period of the Periodic Table are given below:
Li, Be, B, C, N, O, F
(i) Explain why atomic radius decreases from Li to F.
(ii) Identify the most metallic and non-metallic elements among the above elements.

Explanation

(i) On moving from left to right along a period of the Periodic Table, atomic number increases, i.e., number of protons and electrons increases which ultimately increases the nuclear charge. Hence, the electrons are pulled in closer to the nucleus which leads to contraction of the atom and thus atomic radius is decreased. (ii) On moving from left to right in a Periodic Table, metallic character decreases and non-metallic character increases. This is because the capacity to lose electrons from outermost orbit of an atom (called ionisation energy) decreases. Hence, among the above elements Li being placed on extreme left side is most metallic and F being placed on extremely right side is most non-metallic element.