Scientists and their atoms

Democritus

460

460 BC.
• Claimed that everything is made up of atoms• Atoms are indestructible• Atoms are solid

Dalton

Nov 21, 1803

• 1. All matter is made of atoms that can be combined.• 2. Atoms of the same elements are exactly alike• 3. atoms of different elements are different• 4. Atoms of two or more elements can be combined to form different

Thomson

Nov 21, 1897

• Atoms were not simple solid spheres.• He discovered the electrons.

Rutherford

Nov 21, 1911

• Atoms are mostly made of space• The atoms had a small dense positively charged center• He called the center of the atom the nucleus.• The nucleus is tiny• All of an atoms positively charged particles were in the nucleus• Negatively charged particles were on the perimeter of the aotm.

Bohr

Nov 21, 1913

• Proposed that electrons orbit around the nucleus• Made his discovery a couple of years after Rutherford.• Each electron has a fixed amount of energy.• Electrons orbit in energy levels forming rings around the nucleus• The energy levels in his model can be compared to a ladder.• An electron can move between energy levels.

Heisenberg

Nov 21, 1925

• Electrons do not travel in neat orbits.• Electrons contain photons• Included quantum mechanics

Schrodinger

Nov 21, 1926

• Took the model of the atom a step further• He used math to describe the likelihood of finding an atom in a certain position. • Introduced to concept of sub- energy levels

Chadwick

Nov 21, 1932

• He discovered the neutron in 1932