CBSE Class 10 Science 2020 · Paper 31/2/2 · Question 17

(a) (i) $\text{BA}$, that is $\text{HF}$: B is hydrogen (group 1, valency $1$) and A is fluorine (group 17, valency $1$). (ii) ${\text{B}}_2\text{C}$, that is ${\text{H}}_2\text{S}$: C is sulphur (group 16, valency $2$). (b) No, none of the three elements is a metal. A and C lie on the right-hand side of the periodic table and gain electrons ($7$ and $6$ valence electrons), as non-metals do, and B is hydrogen, a non-metal, even though it is placed in group 1. None of them shows the properties of a metal.