Question

The atomic number of three elements $A,B$ and $C$ are $a,a+1$ and $a+2$ respectively. If $C$ is an alkali metal, then the nature of bonding in the compound of $A$ and $C$ is __________.

• A. co-ordinate
• B. covalent
• C. ionic
• D. metallic

Answer 1

Answer: (C)

ionic

$C$ is an alkali metal with atomic number $a+2$. Hence, $B$ with the atomic number $a+1$ must be an inert gas. Because on moving towards right of the periodic table from alkali metals family i.e. from s-block elements we reach at inert gas family series that is at ${18}^{th}$ group.

Thus, the element $A$ with the atomic number $a$ must be an element belonging to the halogen group, because it comes before inert gas group.

Since halogens are non-metal and with alkali metals they will form ionic bonding.