Question

select the correct statement(s) about atomic and ionic sizes below.

au3+ is smaller than au+
na+ is smaller than na
none of the above

Explanation:

When an atom loses an electron to form a cation, the ionic radius is smaller than the atomic radius. For \(Na\) and \(Na^{+}\), \(Na\) has one more electron shell (\(n = 3\) for \(Na\), \(n=2\) for \(Na^{+}\)) so \(Na^{+}\) is smaller. For \(Au\) and \(Au^{3 +}\), \(Au^{3+}\) has lost three electrons. The effective nuclear charge increases (more protons pulling on fewer electrons), so \(Au^{3+}\) is smaller than \(Au^{+}\) (since \(Au^{+}\) has lost only one electron).

Answer:

\(\text{Na}^{+}\text{ is smaller than Na}\), \(\text{Au}^{3 +}\text{ is smaller than Au}^{+}\)