Bosonic Nuclei

Factual Questions
1

I’ll basically keep this short: I have a question about bosonic nuclei, and hopefully I’m not overlooking something simple.

A Helium-4 nucleus has 2 protons and 2 neutrons. Each of these particles has a 1/2 integer spin, but as a composite the total spin is an integer so it is a boson.

The question is: why is sodium-23 bosonic and potassium-40 fermionic? Shouldn’t particles with an even mass number be bosonic and particles with an odd mass number fermionic? What am I overlooking here?

Thanks.

2

I think you have to count the electrons too.
Bosonic Na 23 has 11 protons, 12 neutrons, and 11 electrons, totalling an even 34.
Fermionic K 40 has 19 protons, 21 neutrons an 19 electrons, totalling an odd 59.

3

And that would be what i overlooked. Thanks!

QED

4

Since there should be equal electrons to protons, wouldn’t just counting the Neutrons and seeing if they were odd or even work just as well?

5

Sure. The periodic table gives you proton number though, so you have to subtract that from the mass to get neutrons. That leaves you with all three particle numbers; unless some wily scientist has removed an electron from your potassium 40, and turned it into a boson. :wink: