From the elements of second period of the modern periodic table given below, answer the following questions :[The second-period elements are Li, Be, B, C, N, O, F and Ne.](a) Name the elements in which both the shells are completely filled with elect…

Answer: (a) Neon (Ne); (b) Beryllium (Be); (c) Lithium (Li).

(a) Neon has the electronic configuration 2, 8. Its K and L shells are both completely filled, so it is a noble gas and is chemically inert.

(b) Beryllium has the configuration 2, 2, i.e. 2 electrons in the K shell and 2 in the L shell, so both the shells have the same number of electrons.

(c) Lithium (2, 1) has only one valence electron which it loses easily, so it is the most electropositive element of the second period. Electropositive character decreases from left to right in a period.