How did quantum mechanics change our understanding of atoms

1 Answer. IF we look at the shell model we get a very 2d view , T he quantum mechanics make us realize there is a lot more to realizing the location of an electron. The big change in understanding that happened with Quantum Physics is the idea that the universe is random, rather than clockwork, at its lowest level

No. an alpha particle is a pair of protons and a pair of neutrons, i.e. a helium