Metal A is Sodium (Na) : 2,8,1
Metal B is Calcium (Ca) : 2,8,8,2.
Metal A (Sodium) is more reactive than metal B (Calcium).Reaction: -
i. Sodium metal reacts violently with dilute hydrochloric acid to form sodium chlorides and hydrogen.
2Na(a) + 2HCl(aq)→ 2NaCl(aq) + H2(g)
ii. Calcium reacts less vigorously to form calcium chloride and hydrogen.
Ca + 2HCl → CaCl2 + H2