Here's why:
* Electrons are fundamental particles with a very small mass. They are considered almost massless compared to protons and neutrons.
* Protons and neutrons are made up of smaller particles called quarks, which are also much heavier than electrons.
While photons, which are light particles, are involved in the interactions between atoms (like light absorption and emission), they are not technically *part* of the atom itself.
Let me know if you have any other questions about atoms or particles!
