Question

How do we know that things are generally made up of atoms?

Answer 1

The discovery of the electron suggested there was more to learn about atoms
Because Thomson found that he could actually steer the beams of electrons with magnets and electrical fields, he knew they weren’t just weird rays of light – they had to be charged particles.
And if you’re wondering how these electrons could go flying around independently of their atoms, that’s because of a process called ionisation, in which – in this case – an electrical charge changes the atom’s structure by pushing those electrons off into the space around.
In fact, it’s because electrons are so easily manipulated and moved around that electrical circuits are possible. Electrons in a copper wire travel in a train-like motion from one atom of copper to the next – and it’s that which carries the charge through the wire to the other end. Atoms, it’s worth noting again, are not solid little pieces of matter, but systems that may be modified or undergo structural changes.