Question

An electron in the N shell can have which of the following quantum numbers?

A. s=12.

B. l=1

C. ml=4

D. n=−4

E. ml=−3.

	A and C
	B and C
	C and D
	A, B and C
	A, B and E
	D and E

Answer 1

The old notation of K, L, M and N correspond to principle quantum number n = 1,2,3 and 4 respectively.

After this the rules for quantum numbers apply. The azimuthal quantum number (l) can have values from 0 to n-1. The magnetic quantum number (Ml) can have whole number values from -l through to +l.

The spin quantum number (Ms) can have one of two values, -½ or +½.

With n = 4, l can have the values {0, 1, 2 or 3}, Ml can have the values {-3, -2, -1, 0, 1, 2 or 3} depending on the value of l. Ms can have the values {-½ or ½}.

A. In your example, s is not a quantum number, but if I assume Ms is meant then 12 is not a valid number. It might be valid if the intention is to represent ½ .

How about you look carefully at the question and make sure you are putting it down here in the right format.
B. l=1 is a valid quantum number for a p orbital
C ml = 4 is not a valid quantum number if n = 4
D n = -4 is not a valid quantum number. It might be valid if you actually intended +4. How about you look carefully at the question and make sure you are putting it down here in the right format.
E. ml = -3 is negative but still a valid quantum number.

Option B and E are the only clearly valid quantum numbers. I reserve judgement on the others only on the ground they may have been copied into the question here incorrectly (e.g. option A and possibly option D).