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

IA IIA IIIA IVA VA VIA VIIA VIIIA

E+ E2+ E3+

E4+

Or

E4-

E3- E2- E1- None

Li+ Be2+ B+

C4+

Or

C4-

N3- O2- F- --

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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 Formula Name

CH3COO- Acetate

NH4+ Ammonium

HCO3- Bicarbonate

CO32- Carbonate

CIO3- Chlorate

CrO42- Chromate

OH- Hydroxide

NO3- Nitrate

NO2- Nitrite

PO43- Phosphate

SO42- Sulphate

SO32- 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 2nd Element in a Binary MoleculeName: Nomenclature:

Bromine Bromide

Carbon Carbide

Chlorine Chloride

Fluorine Fluoride

Hydrogen Hydride

Iodine Iodide

Nitrogen Nitride

Oxygen Oxide

Phosphorus Phosphide

Sulphur Sulphide

Prefixes for the # of Atoms

Number of Atoms: Prefix:1 Mono-2 Di-3 Tri-4 Tetra-5

Penta- 6 Hexa-7

Hepta- 8 Octa-9 Nona-10 Deca-

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

3H2 + N2 → 2 NH3

Microscopic Recipe:

3 molecules H2 + 1 molecule N2 → 2 molecules NH3

Macroscopic Recipe:

3 mol H2 + 1 mol N2 → 2 mol NH3

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 H2 react with 1 molecule (mole) of N2

• 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 NH3

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