Question

Why don't atoms collapse if they are mostly empty space?​

Answer 1

Atoms are not mostly empty space because there is no such thing as purely empty space. Rather, space is filled with a wide variety of particles and fields.

Answer 2

Answer:

If atoms were mostly empty space, we could remove this space and shrink atoms. In reality, atoms do not contain any empty space. Rather, they are filled completely with spread-out electrons, making the shrinking of atoms impossible.