Chemistry- Atoms 8vo

atomic theory, parts of the atom, periodic table etc.

Democritus

Proposed that all matter is made of tiny,invisible, indestructible particles called atoms.

John Dalton

Proposed that all matter is made of invisible particles called atoms, which are identical for a given element but different for other element; atoms can’t be created nor destroyed but rearranged in reactions; and compounds form from atoms joining in simple whole-number ratios.

JJ Thomson

Proposed that an atom is a sphere of uniform, diffuse positive charge with tiny, negatively charged electrons embedded within it, like plums in a pudding or seeds in a watermelon.

Where does the name Plum Pudding Model come from?

The model looks like plums in a pudding, seeds in a watermelon or chocolate chips in a chocolate chip cookie.

Invented the Quantum Mechanical Model

Louis de Brogile, Erwin Schrodinger and Heisenberg

1803-1804 and model name

John Dalton with plane circle

Proposed that electrons orbit a nucleus in fixed, quantized energy levels (shells) rather than spiraling in orbit.

Neils Bohr

What was wrong about John Daltons theory?

elements have different atoms, the only thing that stays the same is the number of protons which dictate the atom’s identity.

Proposed that atoms have a tiny, dense, positively charged center (the nucleus) containing most of the mass, with light, negatively charged electrons orbiting at a distance, much like planets around the sun, with most of the atom being empty space.

Ernest Rutherford

plane circle

Democritus and John Dalton

Planetary Model

Neils Bohr

Louis de Brogile, Erwin Schrodinger and Heisenberg

Proposed that particles like electrons exhibit both wave and particle properties (wave-particle duality), described by Schrodinger’s wave equation, which predicts electron probability clouds (orbitals), and quantified by Heisenberg’s Uncertainty Principle, stating we can’t know exact position and momentum simultaneously, forming the modern view of the atom.

400 BCE and model name

Democritus with the plane circle

nuclear model

Ernest Rutherford, big circle (nucleus) with “squiggles” (orbits) and tiny circles (electrons) surrounding it.

mid- 1920’s and model name

Lous de Brogile, Erwin Schrodinger and Heisenberg with the Quantum Mechanincs model

1913 and model name

Neils Bohr with the Planetary model

1897-1904 and model name

JJ Thomson with the Plum Pudding Model

isotopes

atoms of the same element with different amounts of neutrons and mass

average atomic mass

weighted average mass of naturally occurring isotopes