# Does nucleus in an atom spin?

does nucleus in an atom spin?

Simon Bridge
Homework Helper
Depends what you mean by "spin" - the nucleus carries a net angular momentum.

Some nuclei carry a spin. Some don't

Sub-atomic particles are described using the same words we use for everyday things. The meaning of the words we use are NOT the same. Spin, as applied to electrons, photon, or even atoms (and their nuclei) does NOT mean the same thing as a gyroscope spinning, or the Earth spinning, or an ice skater. It isn't correct to picture the nucleus of an atom as a little clump of balls (neutrons and protons) stuck together. The natural tendency is to think of these things as very small versions of things we are familiar with (balls, rocks, sand particles,...) but it will, sooner or later, lead you astray. A sub-atomic entity has two characteristics: orbital angular momentum and spin angular momentum which sum to the total angular momentum (actually, these aren't "characteristics", they are operators). For an atomic nucleus, the spin may be zero or non-zero, but is quantized. This spin can (hypothetically) be used, together with the orbital angular momentum to calculate the spin (as you understand the term) of macroscopic objects (ice skaters, gyroscopes, and planets), but it isn't the same thing. Best answer to your question: some do, some don't- only isotopes with an odd number of nucleons have non-zero spin. (But isotopes with an odd number of BOTH neutrons and protons are in a spin superposition, and we've fallen down the rabbit hole into Quantum Mechanics, sorry!).

Best answer to your question: some do, some don't- only isotopes with an odd number of nucleons have non-zero spin.
Not quite. Isotopes with even number of nucleons may also have non-zero spin, but only isotopes with even number of nucleons may have zero spin.
(But isotopes with an odd number of BOTH neutrons and protons are in a spin superposition, and we've fallen down the rabbit hole into Quantum Mechanics, sorry!).
Are you sure about that? What happens when you send those isotopes through a Stern-Gerlach aparatus?

Simon Bridge
Homework Helper
It's an interesting diversion - oft followed.
But how does it help with the question that was posed in post #1? vis:
does nucleus in an atom spin?
To answer this question properly, we need to know how OP is thinking about it - there are several possibilities.
eg. it is not normally useful to think of an atomic nucleus as spinning in the same sense as one may spin a basketball.

@M.Kalai vanan: the ball is in your court now.
Any of this useful to you?