In a ground state atom of krypton (Kr), how many electrons have the angular momentum quantum number l = 2?

• A. 10
• B. 6
• C. 12
• D. 14

Answer: (A)

Verified step by step guidance

1. Recall that the angular momentum quantum number \(l\) corresponds to the shape of the atomic orbital: \(l=0\) is an s orbital, \(l=1\) is a p orbital, \(l=2\) is a d orbital, and \(l=3\) is an f orbital.
2. Identify the electron configuration of krypton (Kr), which has 36 electrons. The ground state electron configuration is \$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6$.
3. Determine which orbitals have \(l=2\). Since \(l=2\) corresponds to d orbitals, only electrons in the 3d subshell contribute to this count.
4. Count the number of electrons in the 3d subshell from the configuration. The 3d subshell has \$10\( electrons, as indicated by \)3d^{10}$.
5. Conclude that the number of electrons with angular momentum quantum number \(l=2\) in a ground state krypton atom is the number of electrons in the 3d subshell, which is 10.