CLEP Chemistry EXAM LATEST QUESTIONS AND CORRECT DETAILED ANSWERS | AGRADE
John Dalton - ANSWER>> Proposed that matter is composed of atoms; these atoms have different
identities called elements, which combine to form compounds; measured masses of reactants and
products.
J.J. Thompson - ANSWER>> Observed deflection of particles in a cathode ray tube; proposed that atoms
are composed of positive and negative charges; developed the plum pudding model of the atom
Robert Millikan - ANSWER>> Calculated the charge-to-mass ratio of electrons using oil drops falling in an
electric field; surmised the charge of a single electron
Ernest Rutherford - ANSWER>> Used the deflection of alpha particles in a cathode ray tube to discover
that most of the atom is empty space, with protons and neutrons centered in the nucleus.
Niels Bohr - ANSWER>> Determined that electrons exist around the nucleus at a fixed radius; electrons
with higher energy exist farther from the nucleus. Electrons give off electromagnetic radiation when
moving between energy levels.
Max Planck - ANSWER>> Determined that energy is quantized, or composed of discrete bundles.
6.63 x 10^-34 J*sec - ANSWER>> Planck's Constant (h)
3.00 x 10^8 m/sec - ANSWER>> Speed of Light (c)
E = hv - ANSWER>> Energy of a Photon Formula (1)
E = hc / wavelength - ANSWER>> Energy of a Photon Formula (2)
Louis DeBroglie - ANSWER>> Combined Einstein's relationship between mass and energy and the
relationship between velocity and the wavelength of light. All particles with momentum have a
corresponding wave nature.
Wavelength = h / mv - ANSWER>> Wavelength of Particles Formula
Heisenberg's Uncertainty Principle - ANSWER>> It is impossible to simultaneously know the position and
momentum of an electron.
Erwin Schrodinger - ANSWER>> Attributed a wave function to electrons, describing the probability of
where an electron might exist.
Orbitals - ANSWER>> Regions of high probability where electrons might exist; broken into four levels: s,
p, d, or f
Atomic Mass - ANSWER>> The cumulative mass of all the particles in the atom; found by adding the
masses of the protons and neutrons0