Electron configuration | Quantum Theory and Atomic Structure

sulfur: Z = 16 ⇒ 16 electrons
electron configuration: 1s²2s²2p⁶3s²3p⁴

The closest noble gas to sulfur is argon (1s²2s²2p⁶3s²3p⁶)
Sulfur needs to gain 2 electrons to have the same electronic configuration than argon
The most likely ion formed from sulfur is S^2- and its electronic configuration is 1s²2s²2p⁶3s²3p⁶

iron: Z = 26 ⇒ 26 electrons
electron configuration: 1s²2s²2p⁶3s²3p⁶4s²3d⁶
Fe²⁺ ⇒ loss 2 electrons ⇒ electron configuration: 1s²2s²2p⁶3s²3p⁶4s⁰3d⁶