B is a noble gas. He thinks as below about his neighbors. Which of these are correct?
(a) 'D' is an alkaline earth metal
(b) 'C' exists in +2 oxidation state
(c) 'A' has higher electron affinity
It is given that B with atomic number Z is a noble gas.
Atomic number Z-1 would correspond to group 17 elements i.e. halogens. We know that halogens have higher electron affinity. Thus 'A' has high electron affinity.
Atomic number of Z+1 would correspond to group 1 elements i.e. alkali metals, the oxidation number of which is +1. Thus 'C' has +1 oxidation state.
Atomic number of Z+2 for element D would corresponding to group 2 elements i.e. alkaline earth . The oxidation is +2.
Therefore statements (a) and (c) are correct.