Answer:
The electron domain and molecular geometry of NF₃ are option b
Explanation:
First of all, think the total valence electrons of each element.
N : 5
F: 7, but we have 3, so 7.3 = 21
Total: 26 e⁻
Now let's draw a scheme
F ---- N ---- F
|
F
We have to put 26 e⁻ around the elements, so 6 e⁻ are been used for the bonds N-F, so now, there are 20 e⁻ to add. As the F, have used 1 e⁻ to form the bond, there are 6 more, around. Each fluorine which has 7 e⁻, shares 1e⁻ with the N, to complete the octet rule.
So, there are still 2e⁻ to add. They will be above the N and they are free. That's why the molecular geometric is trigonal, and the electronic geeometry is tetrahedral because the non-binding electron pair of N
