Why He, Ne and Ar called inert gas?

Give the symbols for:

(i) a metal of group 2

(ii) a metal of group 13

(iii) two non-metals of group 16

(iv) most reactive non-metal group 17.

Why is K more reactive than Li?

Which one has larger atomic size– Cl or Br? Why?

Where in period 3 of the modern periodic table do we find:

(a) non-metals?

(b) elements forming negative ions?

(c) elements with high melting points?

(d) elements forming positive ions?

(e) metals?

(f) elements with low boiling points?

Mention their atomic numbers only.