The position of three elements A, B and C in the Periodic Table are shown below-

Group $16$	Group$17$
-	-
-	A
-	-
B	C

(a) State whether A is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B?
(d) Which type of ion, cation or anion, will be formed by element A?

(a) $A$ belongs to group $17$. There are $7$ electrons in its valance shell. Therefore it tend to accept one electron to complete octet. Hence, it is a non-metal.

(b) $C$ is less reactive than $A$. As both elements belong to same group and going down to group size of element increases. $A$ is a smaller than $C$ therefore the cloud of electron density surrounding the nucleus is more compact. The stability of completing the octet for $A$ is greater than for $C$ as $A$ is more keen to obtain an electron than $C$.

(c) $C$ is smaller than $B$. $C$ and $B$ belongs to same period. Atomic radius decreases from left to right within a period. This is caused by the increase in the number of protons and electrons across a period. One proton has a greater effect than one electron; thus, electrons are pulled towards the nucleus, resulting in a smaller radius.

(d) $A$ will form anion $A^{-}$. $A$ belongs to group $17$. There are $7$ electrons in its valance shell. Therefore it tend to accept one electron to complete octet and forms anion.