What is the ground-state electron configuration of phosphorus (P), atomic number 15?

• A. $1^{s}22^{s}22^{p}63^{s}23^{p}5$
• B. $1^{s}22^{s}22^{p}63^{s}13^{p}4$
• C. $1^{s}22^{s}22^{p}63^{s}23^{p}3$
• D. $1^{s}22^{s}22^{p}63^{s}23^{p}6$

Answer: (C)