Download Worksheet 3.1 People Who Helped Develop the Modern Model of

Worksheet 3.1
People Who Helped Develop the Modern Model of the Atom
Empedocles: Greek philosopher, thought all matter was made of the 4 elements:
earth, wind, fire, water
Democritus: Greek philosopher, thought all matter was divisible into tiny, indivisible
particles he called “atoms”. Purely speculative.
John Dalton: Scientist, first to show scientifically the idea of atoms, and came up with
the Law of Definite Composition and the Law of Multiple Proportions.
J.J. Thomson: discovered the electron, discovered that the atom was NOT the
smallest particle, and developed the “plum pudding” model of the atom, where the
positive and negative charges were evenly distributed.
Ernest Rutherford: shot alpha particles through thin gold foil to show that the mass of
the atom was concentrated in the middle, or nucleus, which is where the proton
are.
Niels Bohr: studied the line spectrum of elements to find that the electrons exist in
orbits, where only certain, specific energy levels are possible (the electron’s
energy levels are ‘quantized’). His model of the atom has electrons traveling
around the nucleus in orbits, similar to planets around the sun.
Erwin Schrödinger: based atomic model on statistics and probability. Replaced
Bohr’s orbits with “orbitals” or “clouds” of various shapes (s, p, d, f).
James Chadwick: found the neutron.