The transition metals (with the exception of Zn, Cd and Hg) are very much hard and have low volatility. Why Zn ,Cd and Hg has low melting points. (a) These have all their electrons paired. (b) These have maximum number of unpaired electrons. (c) These have very strong metallic bonding. (d) These have more metal-metal bonding.

Zn ,Cd and Hg has low melting points because - These have all their electrons paired.

Explanation:

These have all their electrons paired -: All the electrons in the d-subshell are combined with Zn , Cd and Hg. The metallic bonds present in them are, therefore, weak. This is why they have low points of melting and bolting. therefore , this statement is true. These have maximum number of unpaired electrons. Since , these transition metals have all electrons paired , so this statement is incorrect.These have very strong metallic bonding -: Zn, Cd and Hg d-orbital are completely filled. They have poor metallic bonding and less compact packing due to their fully filled d-orbitals, so all of them are volatile in nature. Therefore, this statement is also not valid .These have more metal-metal bonding. -: Since , their metallic bond is weak , so this statement is not true .

Hence , the correct option is A (These have all their electrons paired).

Molten lead bromide

Explanation:

PbBr 2(l), is an electrolyte. During electrolysis: Pb 2+ ions gain electrons at the cathode and become Pb atoms. Br - ions lose electrons at the anode and become Br atoms, which pair up to form Br 2 molecules.