the center of an atom; made up of protons and neutrons
nucleus
a positively charged subatomic particle in the nucleus of an atom
proton
a neutral subatomic particle in the nucleus of an atom
neutron
a tiny negatively charged subatomic particle moving around outside the nucleus of an atom
electron
any of the possible energies an electron may have in an atom
energy level
a region in an atom where there is a high probability of finding electrons
orbital
an electron in the outermost energy level of an atom
valence electron
properties of elements tend to change in a regular pattern when elements are arranged in order of increasing atomic number, or number of protons in their atoms
periodic law
a horizontal row of elements in the periodic table
period
a vertical column of elements in the periodic table
group(family)
the process of adding electrons to or removing electrons from an atoms or group of atoms
ionization
an atom or group of atoms that has lost or gained one or more electronsand therefore has a net electric charge
ion
an ion with a positive charge
cation
an ion with a negative charge
anion
the number of protons in the nucleus of an atom
atomic number
the total number of protons and neutrons in the nucleus of an atom
mass number
any atoms having the same number of protons but different numbers of neutrons
isotopes
a quantity equal to one-twelfth of the mass of a carbon-12 atom
atomic mass unit(amu)
the weighted average of the masses of all naturally occuring isotopes of an element
average atomic mass
the elements that are good conductors of heat and electricity
metals
the elements that are usually poor conductors of heat and electricity
nonmetals
the elements hat are intermediate conductors of heat and electricity
semiconductors
the highly reactive metallic elements located in Group 1 of the periodic table
alkali metals
the reacive metallic elements located in Group 2 of the periodic table
alkaline-earth metals
the metallic elements located in Groups 3-12 on the periodic table
transition metals
the highly reactive elements located in Group 17 of the periodic table
halogens
the unreactive gaseous elements located in Group 18 of the periodic table
noble gases
the SI base unit that describes the amount of a substance
mole
the number of particles in 1 mole; equals 6.022x1023/mol
Avogadro's constant
the mass in grams of 1 mol of a substance
molar mass
a ratio equal to one that expresses the same quantity in two different ways