Question

Which of the following has the smallest size ?

• A. $Na^+$
• B. $Mg^{2+}$
• C. $Al^{3+}$
• D. $P^{5+}$

Answer 1

Answer: (D)

$P^{5+}$

Answer 2

$Na^+ , Mg^{2+}, Al^{3+}$ and $P^{5+}$ are the isoelectronic species i.e., having same number of electrons but different charges. The size of such species decreases with increasing nuclear charge because the attraction for the electrons increases. Thus, $P^{5+}$ is smallest in size