Final answer:
Oxygen (O) option (a) has two unpaired electrons, determined by its electron configuration 1s² 2s² 2p´. Neon (Ne) has no unpaired electrons as it has a filled valence shell. Sulfur (S) also has two unpaired electrons, but only oxygen is provided as an option in the question.
Step-by-step explanation:
To determine which of the listed elements has two unpaired electrons, we need to look at their electron configurations. Oxygen (O) has the electron configuration 1s² 2s² 2p´, which indicates that it has two unpaired electrons in its p orbitals.
Neon (Ne) is a noble gas with a filled valence shell, meaning it has no unpaired electrons. Sulfur (S) has the electron configuration 1s² 2s² 2p¶ 3s² 3p´, so it has two unpaired electrons as well. Magnesium (Mg), with its electron configuration [Ne]3s², has a filled s subshell and thus does not have any unpaired electrons.
Therefore, both sulfur and oxygen have two unpaired electrons, but because only one answer can be correct in a multiple-choice question like this, and sulfur is not an option provided, the answer is a) O, oxygen, which has two unpaired electrons.