Which of the following is not an electrophile?

Correct answer: (a) Na+

Explanation

Electrophiles are electron-deficient species with an empty orbital to accept an electron pair.

BF₃ (incomplete octet on boron) and H⁺ (no electrons) are electrophiles.

Na⁺ is a stable spectator cation with no vacant orbital to accept electrons, so it is not an electrophile.