1. how many unpaired electrons are in the boron atom? this atom is a. paramagnetic b. diamagnetic 2. how…

Explanation:

Step1: Write electron - configuration of boron

Boron (B) has atomic number 5. Its electron - configuration is $1s^{2}2s^{2}2p^{1}$. The 1s and 2s orbitals are filled, and there is 1 electron in the 2p orbital. So, the number of unpaired electrons in boron is 1. Since it has unpaired electrons, it is paramagnetic.

Step2: Write electron - configuration of cobalt

Cobalt (Co) has atomic number 27. Its electron - configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{7}$. In the 3d sub - shell, according to Hund's rule, electrons first fill the orbitals singly. There are 5 orbitals in the d - subshell. So, for 7 d - electrons, 5 electrons will be unpaired in the 5 d - orbitals and 2 will be paired. So, the number of unpaired electrons in cobalt is 3. Since it has unpaired electrons, it is paramagnetic.

Answer:

1. 1, A. Paramagnetic
2. 3, A. Paramagnetic