Atomic Theory & Structure

Democritus

Aristotle

John Dalton

Socrates

He believed matter was made of atoms.

He believed all matter could be broken down to one of the classical elements.

He performed experiments to prove his theories.

He supported Democritus' atomic theory.

John Dalton

Isaac Newton

Dmitri Mendeleev

Marie Curie

Atoms

Molecules

Protons

Electrons

Atoms cannot be broken apart, created, or destroyed.

Atoms of different elements unite in definite ratios to form compounds.

All atoms of an element are identical.

Atoms can be divided into smaller particles.

Assumptions 1 and 2

Assumptions 2 and 3

Assumptions 3 and 4

Assumptions 1 and 3

Electrolysis cell

Cathode ray tube

Mass spectrometer

Electroscope

Electrons travel from the cathode to the anode.

Electrons have a positive charge.

Cathode is negatively charged.

Anode is positively charged.

Electrons are embedded in a positively charged particle cloud

Electrons orbit around a dense nucleus

Electrons are located only at the surface of the atom

Electrons are randomly scattered outside the atom

Gold-foil experiment

Cathode ray experiment

Oil drop experiment

Photoelectric effect experiment

Alpha particles

Beta particles

Gamma rays

Neutrons

Because they were based on philosophical reasoning without experiments

Because they were based on religious beliefs

Because they were based on mathematical calculations

Because they were based on chemical reactions