Atomic Theory

Greek Model

Idea of atom. Democritus - atomos - indivisible

Alchemy

Practiced in Europe, Africa, Asia

beliefs: transmutation of cheaper metals to gold

John Dalton’s Atomic Theory (Billiard Balls Theory)

Theory stated that elements consisted of tiny, indivisible particles called “Atoms”

Elements are pure substances w particular mass, size, and chem behaviour

atoms of diff elements have diff properties

compounds consist of atoms of different elements combined together

in chem reactions, atoms are combined separated or rearranged

J.J Thomson’s Theory (Plum Pudding Model)

Theory stated that an the dough (the atom) is positive while the plums (the electrons) are scattered throughout the atom.

Rutherford

Discovered the nucleus by firing positively charged particles at a very thin sample of gold foil, disproving Thomson’s theory

Chadwick

Discovered the neutron by bombarding beryllium with alpha particles. Carbon atoms were formed, neutrons emitted

Bohr

Discovered that electrons move around the nucleus. And each orbit (energy lvl) represents a different amount of energy 4 electrons in the orbit

• 2 in first orbit

• 8 in 2nd (Hence octet rule)

• orbits closer to nucleus are lower in energy

• Electrons can move from one orbit to another by absorbing or emitting energy, giving rise to specific spectra