An atom has 6 electrons in its outer shell. How many unpaired electrons does it have?

• A. 0
• B. 4
• C. 6
• D. 2

Answer: (D)

Verified step by step guidance

1. Identify the element based on the number of electrons in its outer shell. An atom with 6 electrons in its outer shell corresponds to the element oxygen, which has 6 valence electrons.
2. Recall the electron configuration for the valence shell of oxygen. The outer shell is the 2p and 2s orbitals, with the 2s orbital holding 2 electrons and the 2p orbitals holding 4 electrons.
3. Distribute the 6 valence electrons into the orbitals following Hund's rule, which states that electrons fill degenerate orbitals singly first, with parallel spins, before pairing up.
4. Place 2 electrons in the 2s orbital (paired), then place the remaining 4 electrons in the three 2p orbitals. According to Hund's rule, the first three 2p electrons occupy separate orbitals singly, and the fourth 2p electron pairs up with one of the singly occupied orbitals.
5. Count the number of unpaired electrons by identifying how many orbitals have only one electron. In this case, there will be 2 unpaired electrons in the 2p orbitals.