Which particle contains the same number of protons as neutrons and has the electronic structure of $1s^2 2s^2 2p^6 3s^2 3p^6$?
- A$^{39}_{18}\text{Ar}$
- B$^{40}_{20}\text{Ca}^{2+}$
- C$^{16}_{8}\text{O}^{2-}$
- D$^{32}_{16}\text{S}$
Chemistry 9701 · AS & A Level · Atomic structure