How many unpaired electrons are present in the ground state of a phosphorus atom? a. 3 0.0

3

Explanation:

You need to remember that to measure the number of unparied electrons in an atom you need to undestard its electron configuration, and the electron configuration of phosphorus is 1s2 2s2 2p6 3s2 3p3, just the last state "3p3" have unpaired electron, and because a p state can fits 6 electrons, and here are only 3, that means that those 3 are unpaired.