Answer:
There are a. 1 unpaired of electron
B. 3 unpaired of electrons
C. There aren't any unpaired of electron
Explanation :
A.The electronic configuration of Sodium(Na) is 1s2 2s2 2p6 3s1. In 1s, 2s and 2p orbitals have two electrons so they are paired but in 3s orbital only one electron is present so Sodium has one unpaired electron.
B. As the same for co it has Electronic configuration of
27
1s2 2s 2 2p6 3s2 3p6 3d 7 4s2
C. Since the atomic number for the krypton ( kr ) is 36 so the electronic configuration is
1s1 2s2 2p6 3s2 3p6 4s2 3d10 4p6
