Atomic Number:
Atomic number refers to the number of protons in the nucleus of an atom. This is what dictates the chemical identity of the atom. For example, carbon has an atomic number of 6, therefore each carbon atom has six protons. In the care of a neuutral atom (one which does not carry a charge), the number of equals the number of protons.

Atomic Mass:
Atomic mass refers to the mass of an individual isotope of an element. It is expressed in atomic mass units, where one atomic mass unit (amu) is 1/12 the mass of a C-12 atom.

Atomic Weight:
The atomic weight is the weighted average of the atomic masses of all the isotopes associated with an element. For exxmple, boron consists primarily of B-10 (5 protons and 5 neutrons) and B-11 (5 protons and 6 neutrons). Boron is aproximately 20% B-10 and 80% B-11, and therefor has an atomic weight of 10.81. The atomic weight is the decimal number of for each element repported on the periodic able.

Electron Confuguration:
The distribution of electrons into the orbitals of an atom

Ionization Energy:
First ionization energy referers to the energy required to remove the outermost electron from an atom, forming a +1 ion. This value always decreases top to bottom down a group, and increases moving left to right across a period. It is possible to remove successive electrons from an atom. For example, the second ionization energy refers to the energy required for the removal of a second electron, forming a +2 ion.

Isotopes:
The isotopes of an element have the same number of protons but differ in their number of neutrons. For example, B-10 has 5 protons and 5 neutrons, whereas B-11 had 5 protons and 6 neutrons.