Question

which is the electron configuration for zinc?
1s²2s²2p⁶3s²3p⁶4s²3d⁸
1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰
1s²2s²2p⁶3s²3p⁶4s²3d¹⁰
1s²2s²2p⁶3s²3p⁶4s²3d¹⁰

Explanation:

Step1: Recall atomic number of zinc

Zinc has atomic number 30.

Step2: Follow electron - filling rules

Electrons fill orbitals in order of increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d. The s - subshell can hold 2 electrons, p - subshell can hold 6 electrons and d - subshell can hold 10 electrons.
1s²: 2 electrons. 2s²: 2 electrons. 2p⁶: 6 electrons. 3s²: 2 electrons. 3p⁶: 6 electrons. 4s²: 2 electrons. 3d¹⁰: 10 electrons.
2 + 2+6 + 2+6 + 2+10 = 30 electrons.
So the electron - configuration of zinc is 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰.

Answer:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰ (the third option in the list)