ELI5: Explain Like I'm 5

Spin quantum number

The spin quantum number is a number used to describe an important property of a particle or atom. This number tells us the direction that the particle or atom is spinning in, like spinning around an axis like a top. It is important to know this for some things, such as when we put particles together to make bigger things. It will help us figure out how they fit together so that they work the way that we want them to!