Question

What is an atom called when two stick together

Answer 1

An atom is called the mass number. 

Answer 2

When an atom sticks together it's called: Residual electromagnetic force.

The reason they stick together is because: When the atoms are electrically neutral, but the electrons in one are attracted to the protons in another, and vice versa. That's what causes the Residual electromagnetic force.

I know this because I did some research online.

Hope I helped!

- Amber