Question

Na+ has completely filled K and L shells. Explain.

Answer 1

Hint – An atom of Na has a total 11 number of electrons, as the atomic number of sodium (Na) is 11. Na will become Na+ by losing one electron, so Na+ will have 10 electrons.

Complete answer:
Then write the electronic configuration and explain.
We have been asked to explain that Na+ has completely filled K and L shells.
So, first of all we know that Na has atomic number 11.
Therefore, we can say that-
Number of electrons = 11.
Number of protons = 11.
Now, to become Na+, Na should have a greater number of protons than electrons.
So, Na will lose one electron and becomes Na+.
So, we can say that Na+ has 10 electrons.
So, these 10 electrons will be distributed in the shells.
Electronic configuration of Na+ is-

K	L
2	8

So, we can see from the electronic configuration that 2 electrons are in the K shell and 8 electrons are in the L shell.
Thus, in Na+, K and L shells are completely filled, as the maximum number of electrons that can be there in K and L shells are 2 and 8 respectively. So, a greater number of electrons cannot be accommodated in these shells.

Note- Whenever such types of questions appear, it is very important to know how many electrons can be accommodated in K and L shells. As mentioned in the solution, we found out the number of electrons in Na+ and then we write the electronic configuration of Na+ to know the number of electrons in each shell.