History of Atomic Theory

Dalton

Proposed the first scientifically supported atomic theory in the early 1800's using indirect evidence

Rutherford

Credited with the discovery that atom consists mostly of empty space and there is a positive "nucleus" in the center of the atom

Democritus

Greek philosopher who thought that atoms were small, solid spheres which were indivisible; lived in B.C. and called the spheres "atomos"

Thomson

Discovered electron's charge to mass ratio and first to indicate that an atom can be divided

Aristotle

Early philosopher that believes that matter could be divided infinitely without changing its properties

Millikan

Discovered the charge of an electron to be negative 1 using the Oil Drop Experiment and the mass of an electron to be 1/1840

Proton

The positive particle in the nucleus of an atom; discovered by Rutherford

Neutron

The neutral particle in the nucleus of an atom

Electron

The negative particle that circles the nucleus

Nucleus

The tiny positive core of an atom, contains protons and neutrons

Cathode Ray

Thomson used this lab equipment to discover the existence of electrons

Atom

Smallest particle of an element that has the properties of that element

Gold Foil Experiment

Experiment conducted by Rutherford in which he discovered that the atom is mostly empty space and the atom contains a dense center called the nucleus

Atomic Theory

Developed by Dalton based on indirect evidence. Contains postulates that include that all matter is composed of atoms, atoms cannot be created or destroyed, all atoms of the same element are identical, chemical reactions occur when atoms are rearranged, and compounds are formed by the combination of two or more different kinds of atoms

Chadwick

Discovered the neutron located in the nucleus of an atom

Plum Pudding Model

Model developed by Thomson that shows that negative particles are floating in a positive sea

Crookes

discovered negative particle called electron using cathode rays