Final answer:
D) 1s²2s²2p⁶3s²3p⁶3d⁷
The electron configuration of Co²⁺ is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷, which corresponds to choice D in the options provided.
Step-by-step explanation:
The electron configuration of Co²⁺ can be determined by looking at the electron configuration for cobalt (Co) and then removing two electrons to account for the +2 charge.
Remember that the 4s electrons are lost first when forming d-block ions. The electron configuration of neutral cobalt (atomic number 27) is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁷.
To get the electron configuration for Co²⁺, we remove two electrons from the 4s sublevel, which gives us: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷, corresponding to choice D.