Answer: The element B will have ONE unpaired electron in the p orbital.
Explanation:
The electronic configuration of each given element is as follows.
Atomic number of calcium (Ca) is 20.
Ca: [tex]1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{2}[/tex]
Atomic number of nitrogen (N) is 7.
N: [tex]1s^{2} 2s^{2} 2p^{3}[/tex]
Atomic number of boron (B) is 5.
B: [tex]1s^{2} 2s^{2} 2p^{1}[/tex]
Atomic number of argon (Ar) is 18.
Ar: [tex]1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6}[/tex]
Atomic number of bromine (Br) is 35.
Br: [tex][Ar] 4s^{2} 3d^{10} 4p^{5}[/tex]
Therefore, boron is the only element that have one unpaired electron in the p-orbital.
Thus, we can conclude that element B will have ONE unpaired electron in the p orbital.
