Explanation:
It is given that r = 0.283 nm. As 1 nm =
.
Hence, 0.283 nm = 
- Formula for coulombic energy is as follows.

where, e =
C
= 

= 
- As 1 eV =

So, 1 J = 
Hence, U = 
= 8.9 eV
- Also, 1 J =

=
kJ/mol
Therefore, U =
kJ/mol
= 
Answer:
6 electrons
Explanation:
The principal quantum number n; describes the energy level and here, it is 2.
The azimuthal or secondary quantum number l is given as 1, we are describing the p-orbital
The magnetic quantum number is -1, and we have 3 sub-orbitals here:
It is a 2p-suborbital
So; in each sub orbital we have 2 electrons
The number of electrons that can be described here = 2 x 3 = 6 electrons.