Question

Identify the property that hydrogen (H) and alkali metals (M) have in common.

• A. Hydrogen forms $H^{+}$ and alkali metal forms a $M^{-}$ ion
• B. Both can combine with halogens to form halides (HX and MX)
• C. Both have valency 2
• D. Both of them have low ionisation energy

Answer 1

The correct option is B

Both can combine with halogens to form halides (HX and MX)

The element hydrogen (H) can form hydrogen halides meaning, it can form $H^{+}$ ions in HF, HCl, HBr, etc. It resembles group - I elements, Li, Na, K, etc. as they form $L{i}^{+},N{a}^{+},K^{+}$, etc. in metal halides (LiCl, NaCl, KBr, etc.). So, it can be placed in group - I along with Li, Na, K.
Both hydrogen and other alkali metals have only one electron in their outermost shell (valence shell). So, their valency is 1 (one).
Normally alkali metals have low ionisation energy while hydrogen has high ionisation energy.