Atomic Number (Z): Number of protons in an atom (found on the bottom left of the symbol) (found on top of modified table)
Mass Number (A): Number of protons + number of neutrons (found on top left of the symbol) 
Atomic Weight/Average Atomic Mass: An average of all naturally occurring isotopes (found on bottom of modified table) 
Mosely: X-rays wavelength depends on proton 
Becquerel: Matter containing uranium exposed photographic film 
Pierre and Marie Curie: Uranium and radium 
Periodic Table 
Group/Column/Family: Vertical section with elements of similar properties 
Periods/Row: Horizontal section based on increasing atomic number 
Group 1: Alkali Metals 
Group 2: Alkaline Earth Metals 
Group 6: Chalcogens 
Group 7: Halogens 
Group 8: Noble gases/Stable octet/Inert 
Empirical Formula: Simplest whole number ratio of atoms (always used in ionics) 
Molecular Formula: Tells you how many atoms are actually present 
Structural Formula: Shows how the elements are bonded together 
Ionic: Contains a metal and nonmetal. Large electronegativity difference. Transfers electrons. Forms salts (which are usually solids) 
Covalent: Contains two nonmetals with little or no electronegativity difference. Shares electrons 
Azide: N3
Metals: Positive ions immersed in a sea of mobile electrons 
Review of Naming 
? Always written with empirical formula (lowest whole number ratio) 
? Name the metal and then name the nonmetal with an “ide” (cation then anion) 
? All ionic compounds since they have a metal and a nonmetal, are salts 
 Ex: NaCl (Sodium Chloride), MgBr2 (Magnesium Bromide) 
? Use stock system when there is more than one oxidation number 
 Ex: PbCl4 – Lead (IV) Chloride 
? The old naming has the first oxidation as “ous” and the second as “ic” 
 Ex: FeCl3 (Ferric Chloride), FeCl2 (Ferrous Chloride) 
? 1
 ox. names: Iron (Ferrous), Copper (Cuprous), Tin (Stannous), Gold (Aurous), Lead (Plumbous), Cobalt (Cobaltous), 
Manganese (Managnous), Mercury (Mercurous), Nickel (Nickelous), Chromium (Chromous) 
? The formula for mercurous/mercury(I) is Hg2
 the mass of C-12 = 1 amu or u