Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common.

In which part of a group would you separately expect the elements to have

(a) the greatest metallic character?

(b) the largest atomic size.

Sodium and aluminium have atomic numbers 11 and 13, respectively. They are separated by one element in the periodic table and have valencies 1 and 3 respectively. Chlorine and potassium are also separated by one element in the periodic table (their atomic numbers being 17 and 19, respectively) and yet both have valency 1. Explain.

This question refers to elements of the periodic table with atomic numbers from 3 to 18. In the table below, some elements are shown by letters, even though the letters are not the usual symbols of the elements.

(a) Which of these is

(i) a noble gas

(ii) a halogen

(iii) an alkali metal

(iv) an element with valency 4

(b) If A combines with F, what would be the formula of the resulting compound?

(c) What is the electronic configuration of G?