How many d electrons are present in a neutral cobalt (Co) atom?

• A. 3
• B. 7
• C. 5
• D. 10

Answer: (B)

Verified step by step guidance

1. Identify the atomic number of cobalt (Co), which tells you the total number of electrons in a neutral atom. Cobalt has an atomic number of 27.
2. Recall the electron configuration order and fill the orbitals according to the Aufbau principle, Hund's rule, and Pauli exclusion principle.
3. Write the electron configuration for cobalt: start filling from 1s, 2s, 2p, 3s, 3p, 4s, and then 3d orbitals.
4. Note that the 4s orbital fills before the 3d orbital, so after filling 4s with 2 electrons, place the remaining electrons in the 3d orbitals.
5. Count the number of electrons in the 3d subshell to find the number of d electrons in a neutral cobalt atom.