Explain why cation are smaller and anions larger in radii than their parent atoms?
A cation is smaller than its parent atom because the removal of an electron results in fewer electrons, while its nuclear charge remains the same. The same nuclear charge acts on fewer electrons, pulling them closer to the nucleus. For example, the atomic radius of sodium is 186 pm compared to the ionic radius of 95 pm for .
An anion is larger than its parent atom because the addition of one or more electrons results in increased repulsion among the electrons and a decrease in effective nuclear charge. The net repulsion outweighs the nuclear charge, causing the ion to expand in size. For instance, the ionic radius of the fluoride ion () is 136 pm, whereas the atomic radius of fluorine is only 64 pm.
Explanation
The textbook explains that a cation loses an electron but retains its nuclear charge, leading to a smaller radius. An anion gains electrons, which increases electron-electron repulsion and decreases the effective nuclear charge per electron, leading to a larger radius.