History of the Atom

SCIENTISTS: Democritus 400 BC John Dalton 1803 Dmitri Mendeleev 1860 – organized the elements in the Periodic Table by increasing mass and similar properties J.J. Thomson 1897 (cathode ray) (Hantaro Nagaoka 1904) <- not in the notes nor on the test Ernest Rutherford 1911 (gold metal foil) Niels Bohr 1913 Henry Moseley 1913 - rearranged the Periodic Table by atomic numbers (Louis de Broglie 1924) <- not in the notes nor on the test (Erwin Schrödinger 1926) <- not in the notes nor on the test James Chadwick 1932 Modern atomic theory 1950

ATOMIC THEORY DESCRIPTIONS: Atoms cannot be cut. Atoms are tiny, solid spheres. All matter is made of atoms. When atoms are rearranged, mass is conserved (cannot be created nor destroyed.) All atoms of the same element have the same mass. Atoms of different elements can combine to form compounds. All atoms of the same element do not have the same mass. Atoms contain negative particles, electrons. Atoms have negative charges spread out through an evenly positive sphere, like plum pudding. Electrons orbit the central nucleus like rings around a planet (Hantaro Nagaoka) Atoms have a dense positively charged nucleus in its center. Electrons move randomly in the space around the nucleus. Atoms contain protons in the nucleus. Atoms have electrons in energy levels. Electrons move in spherical orbits at a set distance from the nucleus, usually drawn as rings. Electrons give off light as they jump between energy levels or rings. Electrons move like beach balls on water waves. (Louis de Broglie) Electron clouds show where electrons are most likely found within the atom. Atoms contain neutrons in the nucleus along with protons. Electrons are located in orbitals associated with different energy levels.

*bold type denotes continued part of the modern atomic theory

ATOMIC THEORY DESCRIPTIONS - NOT IN CHRONOLOGICAL ORDER

Try matching with the scientists that believed each.

Atoms contain neutrons in the nucleus along with protons.

Electrons orbit the central nucleus like rings around a planet (Hantaro Nagaoka)

When atoms are rearranged, mass is conserved (cannot be created nor destroyed.)

Electrons move like beach balls on water waves. (Louis de Broglie)

All atoms of the same element have the same mass.

Electrons move randomly in the space around the nucleus.

All atoms of the same element do not have the same mass.

Atoms have a dense positively charged nucleus in its center.

Electrons give off light as they jump between energy levels or rings.

Atoms contain negative particles, electrons.

All matter is made of atoms.

Electrons move in spherical orbits at a set distance from the nucleus, usually drawn as rings.

Atoms have negative charges spread out through an evenly positive sphere, like plum pudding.

Electron clouds show where electrons are most likely found within the atom.

Atoms contain protons in the nucleus.

Atoms cannot be cut.

Atoms have electrons in energy levels.

Atoms are tiny, solid spheres.

Electrons are located in orbitals associated with different energy levels.

Atoms of different elements can combine to form compounds.