Elements A, B,C and D have atomic numbers 11,18,1 and 17 respectively. Give the chemical formulae of the compound formed between: a) A and D
b) B and C

a ) NaCl

b) No compound.

Explanation:

Atomic number of A is 11 , thus it is sodium. It has electronic configuration of 2,8,1 and thus has 1 valence electron and can form .

Atomic number of B is 18 , thus it is argon. It has electronic configuration of 2,8,8 and thus it is an inert gas.

Atomic number of C is 1 , thus it is hydrogen. It has electronic configuration of 1. It can only share electrons.

Atomic number of D is 17 , thus it is chlorine. It has electronic configuration of 2,8,7 and thus has 7 valence electron and can form .

a) A and D :

Here Sodium is having an oxidation state of +1 called as cation and anion is . Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral

b) B and C

As B is an inert gas , it wont combine with C.