Chapter 12, Problem 18A

Interpretation Introduction

Interpretation:

The given statement is to be completed.

Concept introduction:

Negative ions are formed when an atom gains electrons. The atom after gaining the electrons becomes anion.

Answer to Problem 18A

Non-metals form negative ions by gaining enough electrons to achieve noble gas configuration.

Explanation of Solution

This can be seen with an example:

Bromine is a non-metal which belongs to 17^th group.

Electronic configuration of $Br$ according to Aufbau’s Principle is:

  $\left[Ar\right]4s^{2}3d^{10}4p^5$

Thus it has deficiency of one electron to achieve noble gas configuration. So it has tendency to gain one electron and form most stable ion $B{r}^{-}$

Therefore, Electronic configuration of $B{r}^{-}$ :

  $\left[Ar\right]4s^{2}3d^{10}4p^6$

Which is equivalent to krypton.

Conclusion

Thus, non-metal forms anions by gaining electrons.