Question

Which of the following has the least ionic radius?

• A. \(Mg^{+2}\)
• B. \(Na^+\)
• C. \(Si^{+4}\)
• D. \(Al^{+3}\)

Hint:

For related cations, higher positive charge generally means smaller ionic radius.

Answer 1

The Correct Option is C

Concept:
Ionic radius depends on ionic charge and electronic configuration. Generally, higher positive charge pulls electrons more strongly and produces a smaller ionic radius.

Step 1: Compare charges.
The ions given are: \[ Na^+,\ Mg^{2+},\ Al^{3+},\ Si^{4+} \]

Step 2: Effect of increasing charge.
As positive charge increases, the nucleus attracts the electron cloud more strongly. \[ Na^+>Mg^{2+}>Al^{3+}>Si^{4+} \] in terms of ionic radius.

Step 3: Identify least radius.
Thus, \(Si^{4+}\) has the least ionic radius among the given ions. \[ \therefore \text{Correct Answer is (C)} \]