Chapter 3

Law of Conservation of Mass--Established in 1789 by French Chemist Antoine Lavoisier; States that mass is neither created nor destroyed in any ordinary chemical reaction.

Law of Definite Proportions--a given chemical compound always contains the same elements in the same fixed proportion by mass

Law of Multiple Propotions--statement that when two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers

atomic number--the number of protons in the nucleus of an atom.

atomic mass unit (amu)--a unit of mass that is exactly 1/12 the mass of a carbon-12 atom; also 1 gram/ Avogadro's number

mole--the SI unit used to measure the amount of a substance whose number of particles is the same as the number of atoms of carbon in exactly 12 g of carbon-12

Avogadro's Number--6.0221415 x 10^23

Molar Mass--the mass in grams of 1 mol of a substance

Cathode Ray Experiment

When investigators passed a current through the Cathode tube, they noticed that the surface directly opposite the cathode glowed. They hypothesized that the glow was caused by a stream of particles. They also noticed that the ray was deflected by a magnet much like an electric current was. The rays were deflected to a positive charge and away from a negative charge. This led them to believe that there was a certain type of particle that was being emitted. This was supported when J.J. Thomson found that the particles mass in the cathode tube was always the same, even when the metals where changed. Thomson concluded that all of the cathode rays were composed of the same particles, electrons.

Oil-Drop Experiment

Milikan's experiment was used to find the charge of an e-. Using an atomiser, Milikan put oil droplets in a chamber with a hole at the bottom. Some of the droplets fall through a hole in the bottom. Once though this hole, the droplets are exposed to radiation and attach themselves to free e- in the air. Then, two plates at the top and bottom have current passed through them. The top plate is negative. Milikan determined the charge of an e- by the droplets' abilities to overcome gravity when the charge of the top plate was high enough. An e- has a charge of 1.60217646 × 10-19 coulombs.

Rutherford's Gold Foil Experiment

Ernest Rutherford and his associates bombarded a strip of gold foil with fast moving alpha particles. Geiger and Marsden assumed that the partles would pass through the foil with only a small deflection. However, 1 in 8000 particles was actually deflected directly back at the alpha source. This led Rutherford to conclude that the atom was mostly empty space with most of its mass concentrated at a central point, which he called the nucleus.

Chapter 4

Electromagnetic Radiation--the energy associated with electric and magnetic fields; it varies periodically and travels at the speed of light

Electromagnetic Spectrum--range of all possible frequencies of electromagnetic radiation

Wavelength--the distance over which the wave's shape repeats

Frequency--how many waves are made per time interval, measured in Hertz (Hz)

Photoelectric effect--when light shines on a metal surface, the surface emits electrons

Ground State--The condition of an atom, ion, or molecule, when all of its electrons are in their lowest possible energy levels

Excited State--A stationary state of higher energy than the lowest stationary state or ground state of a particle or system of particles

Line-Emission Spectrum--relative intensity of electromagnetic radiation of each frequency emitted by atoms or molecules of that element or compound when they are excited

Heisenberg Uncertainty Priniciple--The position and momentum of a particle cannot be simultaneously measured with arbitrarily high precision

Orbital-- the probability distribution of an electron in a atom or molecule

Principal Quantum Number--indicates the main energy level occupied by the e-

Angular Momentum Quantum Number--indicates the shape of the orbital

Magnetic Quantum Number--indicates the orientation of the orbital around the nucleus

Spin Quantum Number--indicates the fundamental spin states of the e-

Aufbau Principle--an e- occupies the lowest energy orbital that can receive it

Pauli Exclusion Principle--no two e- can have the same set of quantum numbers

Hund's Rule--orbitals of equal energy are each occupied by one e- before any orbital is occupied by a second e- and all e- in singly occupied orbitals must have the same spin

Noble Gas--a family of nonreactive monoatomic gases found on the far right of the periodic table

Noble Gas Configuration--shortened version of electron configuration in which you simply include the closest noble gas (of a smaller atomic number) and list the electron configuration from the next element from the noble gas to the element you are doing the configuration for

The Photo-Electric Effect

In the early 1900s, scientist conducted two experiments that had results that could not be explained by the wave theory of light. One was the Photo-Electric Effect. Scientists observed that even at high intesities, a metal would not emit an electron unless the frequency was correct. This contradicted the theory that light of any frequency could supply enough energy to eject an e-. Scientists began to think that light wasn't just a wave, that it also had mass.