Chapter 18, Problem 4TE

To determine

The size of potassium atom and its ion and conclude which one is larger.

Answer to Problem 4TE

The potassium atom, $\text{K}$, is larger than the potassium ion, ${\text{K}}^{+}$ due to the presence of one more extra shell of electrons.

Explanation of Solution

The electrons of an atom are placed in shells outside the nucleus. The electrons are arranged according to the energy level and the last outer shell of an atom is called the valence shell of an atom. Thus the electrons associated in the valence shell are the valence electrons.

The potassium atom belongs to group 1 and period 4 thus has only one electron in the outermost shell that is the 3^rd shell. To get higher stability, atoms either gain or lose the electrons to attain eight electrons in the outermost shell. Thus potassium atom, $\text{K}$, tends to lose that one electron from the 3^rd shell and complete the octet state configuration of 2^nd shell to form the potassium ion, ${\text{K}}^{+}$.

Thus, the potassium atom, $\text{K}$, is larger due to the presence of an electron in the 3^rd shell whereas the potassium ion, ${\text{K}}^{+}$ is smaller due to the absence of an electron in the 3^rd shell.

Conclusion:

Thus, due to the presence of one more extra shell of electrons the potassium atom, $\text{K}$, is larger than the potassium ion, ${\text{K}}^{+}$.