Final answer:
In a ground state atom of krypton (Kr), there are a total of 10 electrons with the quantum number ℓ = 2, which corresponds to electrons in the 3d subshell.
Step-by-step explanation:
The question asks how many electrons in a ground state atom of krypton (Kr) have the quantum number ℓ = 2. Krypton has an atomic number of 36, which means it has 36 electrons. According to the question, we are interested in the electrons with the quantum number ℓ = 2, which corresponds to the d-subshell. The d-subshell can hold a maximum of 10 electrons because following the formula 2(2ℓ + 1) we get 2*(2*2 + 1) = 2*(4 + 1) = 10 electrons. Since we are looking for the electrons in the ground state, we only consider the filled subshells up to krypton's electron configuration. The electron configuration for Krypton is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s² 4p⁶. In the case of krypton, the n = 3 shell, with ℓ = 2, is the 3d subshell, and it is fully filled with 10 electrons. Therefore, the correct answer is that there are 10 total electrons in a ground state krypton atom that have the quantum number ℓ = 2.