Question
Question: The set representing the correct order of ionic radius is :...
The set representing the correct order of ionic radius is :
A
Na+> Li+> Mg2+> Be2+
B
Li+> Na+> Mg2+> Be2+
C
Mg2+> Be2+> Li+> Na+
D
Li+> Be2+> Na+> Mg2+
Answer
Na+> Li+> Mg2+> Be2+
Explanation
Solution
Down the group, ionic radii increases with increasing atomic number because of the increase in the number of shells. But across the period, the ionic radii decreases due to increase in effective nuclear charge as electrons are added in the same shell. Li+ and Mg2+ are diagonally related but Mg2+ having higher charge is smaller than Li+, so correct order is Na+ > Li+ > Mg2+ > Be2+.
Be2+ = 0.31 Å
Mg2+ = 0.72 Å
Li+ = 0.76 Å
Na+ = 1.02 Å