CLEP Chemistry Latest Update Graded A

CLEP Chemistry Latest Update Graded A John Dalton 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 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 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 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 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 Determined that energy is quantized, or composed of discrete bundles. 6.63 x 10^-34 J*sec Planck's Constant (h) 3.00 x 10^8 m/sec Speed of Light (c) E = hv Energy of a Photon Formula (1) E = hc / wavelength Energy of a Photon Formula (2) Louis DeBroglie 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 Wavelength of Particles Formula Heisenberg's Uncertainty Principle It is impossible to simultaneously know the position and momentum of an electron. Erwin Schrodinger Attributed a wave function to electrons, describing the probability of where an electron might exist. Orbitals Regions of high probability where electrons might exist; broken into four levels: s, p, d, or f Atomic Mass The cumulative mass of all the particles in the atom; found by adding the masses of the protons and neutrons. Units: Atomic Mass Units (AMU) Example: helium = 2 protons + 2 neutrons = 4 AMU Atomic Number The number of protons in the nucleus of an atom, or the total nuclear charge. Also the number of electrons surrounding the nucleus. Isotopes Atoms with the same number of protons but different numbers of neutrons. Example: carbon-12 (6 neutrons) vs carbon-14 (8 neutrons) Atomic Weight Molar mass of the element, or the mass in grams of one mole of atoms Pauli Exclusion Principle No two electrons can occupy the exact same energy level or have the same set of four quantum numbers Quantum numbers 1. Principal (n) 2. Angular Momentum (l) 3. Magnetic (ml) 4. Magnetic Spin (ms) Principal Quantum Number The shell or energy level an electron occupies; values from 1-7. Electrons with higher values are farther from the nucleus. Angular Momentum Quantum Number The subshell