PES spectrum | Quantum Theory and Atomic Structure

3 peaks = 3 subshells
The 3 first subshells of any atom are 1s, 2s and 2p

The highest binding energies corresponds to the core orbitals. Here we have only one core orbital: 1s. 1s is totally filled ⇒2 electrons.
Regarding the relative number of electrons we have 2 electrons in 2s and 3 electrons in 2p.

The electronic configuration of the element represented by the complete PES spectrum is 1s²2s²2p³
This element is nitrogen.