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Atomic Theories Cheat Sheet (DRAFT) by

Scientists and their discoveries for understanding the atomic theory

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Empedocles (500 B.C)

All matter is made up of water, earth, air & fire

Democritus (300 B.C)

Solid Sphere Model
Atoms are indivi­sible, indest­ruc­tible, in motion & differs in shapes and sizes

John Dalton (Early 1800s)

Billiard Ball Model / Solid Sphere Model
Atoms can't be dest­r­oy­ed, subd­i­vi­ded or crea­ted
Atoms of the same element have iden­tical proper­­ties; Atoms from different elements have diff­erent proper­­ties
During chemical reactions, atoms can be rear­r­an­ged, sepa­rated or crea­ted
Atoms are combined in simple whole number ratios

J.J Thompson (Late 1800s)

Plum Pudding Model
Discovered that elec­trons are stuck in a posi­t­ively charged matter
Conducted the cath­o­de-ray experi­­ment; Beta particles were attracted to the positively charged magnets

Ernest Rutherford (1911)

Nuclear Model / Ruther­­ford's Model
Dense, tiny positively charge in the centre of an atom
Several spaces in an atom
Most of the mass is in the nucleus

Max Planck

Proposed that particles can emit a certain amount of elec­t­ro­­mag­­netic radiat­ion
Electrons need to obtain the amount of energy before emitting it
Analogy: Similar to a bank machin­­e...you can only receive multiple of $20.00, although other amounts exit (e.g. $32.00)

Niels Bohr (1913)

Planetary Model / Bohr's Model
Electrons emit phot­ons (small amount) of light that jumps up or down to other shells and doesn't spiral into the nucleus while emitting phot­ons

Werner Heisen­berg's Uncert­ainty Principle

It's impossible to know both the posi­tion (location) & the mome­ntum (speed) of a particle at any given moment

Erwin Schrod­inger (1926)

Quantum Mechanical Model
Mathem­­at­i­cally predicted the regions of space where electrons can be found

De Broglie

Quantum Mechanical Model
Electrons behave like waves & part­icles

Conundrum #1

Electrons in motions should emit energy of a continuous electr­oma­gnetic spectrum (rainbow). This loss of energy would cause electrons to spiral into the nucleus, destroying the atom. This wasn't demons­trated in Ruther­ford's Model, so scientists were skeptical
Electrons in motion doesn't emit a continous electr­oma­gnetic spectrum, but a line spectrum (series of separate lines of different colours of light emitted by atoms of a specific element as they lose quanta) instead. Additi­onally, once Niels Bohr proved how electrons move from shell to shell when quanta is emitted scientists understood why electrons emitting energy wouldn't crush the atom.