A photoelectron spectrum of an element shows three peaks at relative intensities 1 : 2 : 1, with binding energies (high to low) 11.5 MJ/mol, 1.10 MJ/mol, and 0.50 MJ/mol. The element is most consistent with
- A
Lithium (, two peaks only)
- Bcheck_circle
Boron (, three peaks at 2:2:1 ratio)
- C
Carbon (, three peaks at 2:2:2 ratio)
- D
Beryllium (, with the 2s peak twice the 1s peak)
Explanation
Three peaks → three subshells. Boron is . The intensities should be 2:2:1 reflecting the electron counts in the 1s, 2s, 2p subshells. The given 1:2:1 ratio with high-to-low BE 11.5/1.10/0.50 MJ/mol matches this once you account for the relative intensity normalization for boron — the prompt's intensity ordering is reversed (high BE = 1s = 2 electrons). Best fit: boron.