Scientist

John Dalton's Theory

Atoms are tiny, invisible particles Atoms of one element are all the same Atoms of different elements are different Compounds form by combining atoms

J.J Thompson

Discovered electrons First scientist to show that atoms were made of smaller things Proposed the existence of (+) particles "Raisin bun model"

James Chadwick

Discovered neutrons, which have no charge Worked with Rutherford Discovered that neutrons are located in the nucleus

Ernest Rutherford

Discovered protons and the nucleus Showed that atoms have (+) particles in the center, and atoms are mostly empty space Called (+) particles protons, and he called the center of the atom the nucleus

John Dalton

English schoolteacher, performed many experiments on atoms Created the first atomic theory Viewed atoms as tiny, solid ball

Democritus

Greek philosopher, father of modern atomic theory Proposed that matter could not be divided into smaller pieces forever Claimed that matter was made of small, hard particles called "atomos"

Niels Bohr

Improved Rutherford's model Proposed that electrons move around the nucleus in shells (or orbits) Every atom has a specific number of shells

Modern Atomic Model

Work done since 1920 has changed the model New model has electrons moving around the nucleus in a cloud Impossible to know where an electron is at any given time