Given below are two groups showing basic and acid radicals. Based on these two groups, answer the questions that follow :

(a) Which basic radical or cation exhibits variable valency ?

(b) How is NH₄⁺ ion different from other basic radicals in the group ?

(c) Which acid radical or anion is the odd one out in the group ? Justify your answer.

(d) Using one radical from each group, form a compound that is commonly used in daily life. Write its name and chemical formula.

(a) Copper exhibits variable valency. It shows valencies 1 and 2.

(b) NH₄⁺ ion is different from the other basic radicals because it is a polyatomic ion, whereas the others are simple metal ions.

(c) NO₃^- is the odd one out because it is the only polyatomic acid radical in the group. Cl^-, S^2- and O^2- are monoatomic ions.

(d) Using Na⁺ from basic radicals and Cl^- from acid radicals, the compound formed is sodium chloride. Its chemical formula is NaCl.