Detailed Explanation:

Electrophiles are electron-deficient species that accept electron pairs, typically carrying a positive charge or having an incomplete octet.

Na⁺ (sodium ion) has a stable noble-gas configuration (1s²2s²2p⁶) with no empty orbitals available to accept electrons, making it a spectator ion rather than an electrophile.

BF₃ (boron trifluoride) has an incomplete octet on boron (only 6 electrons), allowing it to act as a Lewis acid and electrophile.

H⁺ (proton) has no electrons and readily accepts electron pairs, making it a strong electrophile.