Review of Sec IV Chemistry

Ions An ion is an atom that has become electrically charged by losing or gaining one or more electrons

Most Probable Ions for Group A Elements IAIIAIIIAIVAVAVIA VIIA VIIIA E+E+ E 2+ E 3+ E 4+ Or E 4- E 3- E 2- E 1- None Li + Be 2+ B+B+ C 4+ Or C 4- N 3- O 2- F-F- -- Group # Most Probable Form of Ion Example

Polyatomic Ions A group of two or more chemically bonded atoms that has become electrically charge by losing or gaining one or more electrons

Chemical FormulaName CH 3 COO - Acetate NH 4 + Ammonium HCO 3 - Bicarbonate CO 3 2- Carbonate CIO 3 - Chlorate CrO 4 2- Chromate OH - Hydroxide NO 3 - Nitrate NO 2 - Nitrite PO 4 3- Phosphate SO 4 2- Sulphate SO 3 2- Sulphite

Rules of Chemical Notation 1.Find the symbol of each element in the molecule on the periodic table 2.Determine the order of the symbols: In binary molecules containing a metal and a nonmetal, the metal comes first. In all other cases the order is: B, Ge, Si, C, Sb, As, P, N, H, Te, Se, S, I, Br, O and F

3.Add subscripts after the symbols to specify the # of atoms or ions of each elements in the molecule

To know the subscript the number of the atoms in the molecule must be adjusted so that each atom forms all the bonds to balance their charges

Nomenclature 1.Name the first element 2.Change the name of the second element according to the indication in the following table 3.When applicable, a prefix or prefixes is added to specify the # or atoms of each elements

Some Names for the 2 nd Element in a Binary Molecule Name:Nomenclature: BromineBromide CarbonCarbide ChlorineChloride FluorineFluoride HydrogenHydride IodineIodide NitrogenNitride OxygenOxide PhosphorusPhosphide SulphurSulphide

Prefixes for the # of Atoms Number of Atoms:Prefix: 1Mono- 2Di- 3Tri- 4Tetra- 5Penta- 6Hexa- 7Hepta- 8Octa- 9Nona- 10Deca-

New Stuff: Limiting Reagent Any reactant that is used up first in a chemical reaction; it determines the amount of product that can be formed in the reaction

Cookin with Chem Limiting Reagent is like cooking something but have only a certain amount of ingredients If you were making sandwiches and had a full jar of peanut butter and a full jar of jam but only 6 slices of bread, the bread is limiting how many sandwiches you can make

3H 2 + N 2 2 NH 3 Microscopic Recipe: 3 molecules H molecule N 2 2 molecules NH 3 Macroscopic Recipe: 3 mol H mol N 2 2 mol NH 3

Before: Hydrogen and nitrogen are present in a 3:2 molecule (mole) ratio. The reaction takes place according to the balanced equation where 3 molecules (moles) of H 2 react with 1 molecule (mole) of N 2 At this point all the hydrogen is used up

After: Since all the hydrogen is gone, no more reacting can happen BUT there is still 1 molecule (mole) of un- reacted Nitrogen left There is also now 2 molecules (moles) of NH 3

So….. For this reaction the Hydrogen is the limiting reagent We call the Nitrogen the excess reagent, which is the reactant that there is more than enough of to react with the limiting reagent in a reaction