Chapter 12, Problem 26A

Interpretation Introduction

Interpretation:

The reason for the cations to be smaller than their parent atoms needs to be explained.

Concept introduction:

Cations are formed by loss of electrons.

Answer to Problem 26A

Cations are smaller than their parent atoms because after losing the electrons, ion has less number of electrons but number of protons remains same. Thus, the same nuclear charge has to hold less number of electrons. Therefore, effective nuclear charge increases and the size decrease.

Explanation of Solution

Taking example:

  $N{a}^{+}$ is smaller than $Na$

  $\begin{array}{l}\begin{array}{l}{\text{ Na}}^{+}\text{ Na}\\ \text{Protons 11 11}\end{array}\hfill \\ \text{Electrons 10 11}\hfill \end{array}$

Thus, in $N{a}^{+}$ 11 protons are to hold 10 protons. This increases effective nuclear charge. So size decreases.

Conclusion

Thus, cations are always smaller than their parent atoms.