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500 BCE
Early Ideas about Atoms
The ancient Greek philosopher Democritus and his teacher Leucippus believed that when cutting something in half there was a point where it couldn't be done and Democritus called it "atomos". He claimed that all matter was made of them and they came in different sizes and shapes. -
Dalton's Model of the Atom
John Dalton came up with the first scientific experiments that
showed that matter was made of tiny little particles. He imagined
them sort of as tiny balls that arranged in different combinations to
make different compounds and he imagined that these atoms were indivisible, you couldn't cut them into smaller pieces. -
Plum Pudding Model
JJ Thompson discovered that atoms have electrons, atoms weren't indivisible and he discovered that electrons are much much smaller than atoms. He imagined that splitting an atom open you'd see electrons stuck throughout the inside. Also that negative electrons stuck in like a positively charged dough and together the positive and negative charge balanced the two things balanced balanced each other out so that the atom was electrically neutral. -
Nuclear Model
Ernest Rutherford discovered that Adams had a nucleus that all the positive charge in an atom was concentrated right in its center and that besides that in the electrons atoms were pretty much empty space. Rutherford showed that all this positive stuff was concentrated right in the center and this is called the nuclear
model of the atom because it has a nucleus. -
Bohr Model
Niels Bohr came up with his model of the atom,
he reasoned that there is a nucleus in the atom but electrons instead of just sort of being randomly distributed throughout
the atom, Bohr said that the electrons were spinning around the
nucleus in circular orbits. -
Quantum Mechanical Model
Erwin Schrodinger showed that electrons weren't really spinning
in orbits but it's more like they were hyperactive flies and they were buzzing around the atom sketching out different shapes. Schrodinger called the hyperactive sketch out shapes
he called them orbitals. Chadwick
discovered new Tron's so the really correct view of the quantum mechanical model shows the orbitals being sketched
out by the electrons but then also show the subatomic particles protons and neutrons in the nucleus.
