John Dalton

Dalton is known as the father of the atomic theory. He discovered that elements consist of indivisible, indestructible, small atoms, and different atoms make up different elements and compounds. He came up with these 6 postulates:

All matter consists of indivisible particles called atoms.
Atoms of the same element are similar in shape and mass, but differ from the atoms of other elements.
Atoms cannot be created or destroyed.
Atoms of different elements may combine with each other in a fixed, simple, whole number ratios to form compound atoms.
Atoms of same element can combine in more than one ratio to form two or more compounds.
The atom is the smallest unit of matter that can take part in a chemical reaction.

In Dalton's Model, atoms are balls. Atom balls stick together to form compounds, shown here.

JJ Thomson

Thomson is credited with the discovery of the electron. He came up with the Plum Pudding Model - negative electrons scattered across a jelly-like sphere of positively charged atoms. It was abandoned in 1911 for the Rutherford model.

The plum pudding model included a gelatinous positivly charged blob with negative electrons stuck inside.

Ernest Rutherford

Known as the pioneer of radioactivity and the atom, Rutherford found that there are two different types of radiation (alpha, and beta). He also discovered that Atoms are made up of mostly empty space concentrated in a central area known as the positively charged Nucelus.

The rutherford model did not include much about electrons. The circle included here is to illustrate the space

Neils Bohr

Bohr created the Bohr Model, also known as the Planetary Model, in which the electrons surround the nucleus in pathways known as orbits, each with their own energy levels. It was the first model to use quantum theory.

The 1st energy level can only hold 2 electrons, but the ones after that can hold 8!

Erwin Schrödinger

Schrödinger discovered that electrons live in orbitals around the nucleus. Orbitals are technically electrons AND waves, but practically they're regions where an electron can be. Schrödinger derived a mathmatical equation to determine the probablity that an electron is in a certain place in the orbital: $${\hat{H} \Psi = E\Psi}$$

Orbital around a nucleus (model credit)

Werner Heisenberg

Heisenberg discovered two major things in his career: The strong force, which holds particles in the nucleus together, and the uncertainty principle. The uncertainty principle states that we cannot know the position and speed/direction of a particle at the same time, and it is described in the equation: $$ {\Delta p\Delta s\geq \frac{h}{4\pi}} $$ Where ∆p is the uncertainty in position, ∆s is the uncertainty in momentum, and h is Planck's constant. As our certainty in position goes up, our certainty in speed/direction must go down.