Chapter #7

Chemical Formulas

and Chemical Compoun

ds

NearingZero.net

Section 1Chemical Names and

Formulas• Chemical Formulas

• C6H12O6 Al2(SO4)3

Subscript indicates that there are 6 carbon atoms

Monatomic Ions• Positive Ions1. Write the name of

the element2. Write the word ion

• Na+ = Sodium ion• Transition elements

use Roman Numerals

• Fe +2 = Iron (II) ion

• Negative Ions1. Write the name of

the element2. Change the ending

to –ide3. Write the word ion

• Cl- = Chloride ion

Binary Ionic Compounds

• 2 elements= Binary• Metal + nonmetal = ionic1. Write the name of the 1st element2. Write the name of the 2nd element3. Change the ending to –ide

• NaCl = Sodium Chloride

• MgCl2 = Magnesium Chloride

Stock System• Uses roman numerals1. Write the name of the 1st element2. Write the oxidation number of the 1st

element3. Write the name of the 2nd element4. Change the ending to –ide

• CrF3 = Chromium (III) Flouride

• NiF

Binary Molecular Compounds

• Molecular= covalent PG 212 Prefixes1. Write the name of the 1st element2. Write the name of the 2nd element3. Change the ending to –ide4. Put in prefixes Only use prefixes on the 1st element if it

is more than 1NO2= Nitrogen Dioxide

N2O3

Binary Acids• Acids always begin with H• Acids that consist of 2 elements1. Write hydro2. Write the 2nd element3. Change the ending to –ic4. Write the word ACID• HF= Hydrofluoric Acid• HBr

Oxyacids• Are acids that contain hydrogen, oxygen, and

a third element. Never use Hydro1. Write the name of the polyatomic (pg 210)2. Change the ending to –ic or –ous (ate -ic & ite –ous)1. Write the word ACID• H2SO4 = sulfuric acid• H3PO4

Polyatomic Compounds

1. Write the name of the 1st element2. Write the name of the polyatomic (pg

210)

• NaNO3 = Sodium Nitrate

• AgNO2

Section 2 Oxidation Numbers

• Oxidation numbers- are assigned to the atoms in molecules, including molecular ions, to show the general distributions of electrons among the bonded atoms. +1

+2 +3

+/-

4 -3 -2 -1

Oxidation numbers• Rules pg 2161. UF6

• UF6 criss cross the numbers up

• Check the 2nd element using the periodic table• U= +6 F= -12. Polyatomic compounds do a math line +3 -8 =0 H= +1 P= 5 O=-2 +1 -2 H3PO4

3. If there is an ION (charge) do a math line

Practice oxidation numbers

• GeCl2• CS2

• ClO3-

• H2SO4

• PCl3• HNO3

• GeO• SO4

-2

• NO2-

Section 3 Using Chemical Formulas

• Formula mass (molar mass or weight) of any compound or polyatomic ion is the sum of the average atomic masses of all the atoms represented in the formula.

• H20 H x 2= 2.014g

O x 1 = 15.999g 18.013 g of H2O

Old stuff

• Mole to grams• Grams to moles• Moles to particles• Particles to moles• Grams to particles• Particles to grams

Percent Composition

% comp= Mass of element in the sample

mass of sample (formula mass)

Calculate the % comp of H2O

X 100

Section 4 Determining Chemical Formulas

• Empirical Formula- (simplest formula) consists of the symbols for the elements combined in a compound, with subscripts showing the smallest whole-number mole ratio of the different atoms in the compound.

• C2H6 simplest formula would be CH3

Empirical Formulas1. Drop the % signs and add grams2. Covert to moles of each element3. Take the smallest number of moles

and divide it into all the other values4. Write the formula Determine the empirical formula for a

sample that contains 78.1% B & 21.9% H

Molecular Formulas• Do the same 4 steps for determining

empirical formulas5. Add up the formula mass of the empirical

formula6. Use the molecular formula mass in the

question7. Use the formula X= Molecular formula

mass empirical formula

mass8. Use the x and multiply your empirical

formula using it

• “Cartoon”. Aug. 11, 2006. http://www.nearingzero.net/sbunch5.html