### General Chemistry QBank 4

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**Thu Oct 11, 2018 2:19 pm**A student recently emailed us to ask for clarification on General Chemistry QBank Question 4.

This question asks: "In the ground state of cobalt, how many d orbitals contain at least one electron?" The answer to this question is 5 orbitals. Cobalt's electron configuration is [Ar] 3d^7 4s^2. The 3d subshell has five possible orbitals, each of which can hold up to two electrons. Since there are 7 electrons in the 3d subshell, two orbitals will hold two electrons each (4 total), and the remaining three orbitals will each hold 1 electron (3 total). Remember that according to Hund's rule, each orbital must be half-filled before being doubly occupied by two electrons.

This question asks: "In the ground state of cobalt, how many d orbitals contain at least one electron?" The answer to this question is 5 orbitals. Cobalt's electron configuration is [Ar] 3d^7 4s^2. The 3d subshell has five possible orbitals, each of which can hold up to two electrons. Since there are 7 electrons in the 3d subshell, two orbitals will hold two electrons each (4 total), and the remaining three orbitals will each hold 1 electron (3 total). Remember that according to Hund's rule, each orbital must be half-filled before being doubly occupied by two electrons.