Be's electron affinity is approximately zero because which subshell is fully filled?

Be's electron affinity is approximately zero because which subshell is fully filled?

• A. 2s
• B. 2p
• C. 3s
• D. 1s

Answer: (A)

Electron affinity is the energy change when a neutral atom gains an extra electron. For beryllium, the outermost shell is a closed 2s subshell (1s^2 2s^2). The next available orbital is 2p, which lies at higher energy. Adding another electron would have to go into this higher-energy 2p space and would disrupt the stable, filled 2s subshell, providing little stabilization and often little to no energy release. That’s why Be’s electron affinity is essentially zero—the atom is already in a relatively stable, closed-shell arrangement, and the added electron doesn’t fit into a low-energy, stabilizing orbital.

Electron affinity is the energy change when a neutral atom gains an extra electron. For beryllium, the outermost shell is a closed 2s subshell (1s^2 2s^2). The next available orbital is 2p, which lies at higher energy. Adding another electron would have to go into this higher-energy 2p space and would disrupt the stable, filled 2s subshell, providing little stabilization and often little to no energy release. That’s why Be’s electron affinity is essentially zero—the atom is already in a relatively stable, closed-shell arrangement, and the added electron doesn’t fit into a low-energy, stabilizing orbital.