Answer:
The valid quantum numbers are l=0, l=-2 and l= 2.
Explanation:
Given that,
n = 3 electron shell
Suppose, the valid quantum numbers are
l = 3
m = 3
l = 0
m = –2
l = –1
m = 2
We know that,
The value of n = 3
Principle quantum number :
Then the principal quantum number is 3. Which is shows the M shell.
So, n = 3
Azimuthal quantum number :
The azimuthal quantum number is l.

Magnetic quantum number :
The magnetic quantum number is

Hence, The valid quantum numbers are l=0, l=-2 and l= 2.
ADD THEM all, and then divide by four. Thats what I would do!
Nails are made up of iron not of phosphorus and barium.
As both phosphorous and barium are relatively weaker than iron ,phosphorus breaks easily and barium is also fairly weak. Iron nails are already also not that strong, but their weight and strength are sufficient.
So the nails are made up of iron.