Writing and NamingChemical compounds

Oxidation Numbers

Same as the charge for a monatomic ion (ex. Fluorine is -1, sodium is +1)

In a covalent compound, the electrons are divided equally if the atoms are the same, or are assigned to the more electronegative atom if they are different (H2O has H+1 and O-2

oxidation states) Sum is equal to zero in a compound

Naming Chemical Compounds

Chemical formulas

Show the kinds and numbers of atoms in the smallest representative unit of the substance

Molecular formula – neutral group of atoms, covalently bonded ex. H2O

Formula unit – lowest whole number ratio of ions in an ionic compound ex. NaCl

Metals

Form positive ions Are written first in a

compound Just use their

element names

•

Transition Metals

Have more than one charge

Need to have Roman numerals added to their names to show charge

OR need suffixes to show lower or higher charge (-ous,-ic-)

•

Nonmetals

Form negative ions (or have negative oxidation states)

Are written second in a compound name

Change the element name by adding –ide suffix

•

Naming Binary Ionic Compounds

Binary means two elements Ionic – is a salt, composed of a metal ion and

a nonmetallic ion The element with the positive ionic charge is

written first (Cation = metallic) The negative ion element name gets an ending

of “ide” (Anion = nonmetallic)

45. Name Binary Ionic Compounds

a. ZnS

b. KCl

c. BaO

d. CuBr2

a. Zinc sulfide

b. Potassium chloride

c. Barium oxide

d. Copper II bromide

Writing formulas

Use name to identify symbol and charge for each part of the compound (Roman numbers tell charge)

The sum of the charges for a compound must be zero

Determine how many of each element or polyatomic ion you need

Writing Formulas con’t

Use subscripts if you need more than one of any part

If there is more than one polyatomic ion, use parentheses and put the subscript outside the parentheses

Example magnesium nitrate Mg +2 NO3

– becomes Mg (NO3)2

Ionic Compounds

# 44 Binary Ionic compounds

a. Sodium iodide

b. Stannous fluoride

c. Potassium sulfide

d. Calcium iodide

a. NaI

b. SnF2

c. K2S

d. CaI2

Binary Ionic Examples

Copper I oxide Copper II oxide Ferrous chloride Ferric chloride Lead II sulfide Lead IV sulfide

Polyatomic ions

Atoms form charged groupsMost are negatively chargedThey combine with other elements or

polyatomic ions to form compoundsThey stay together (like a close group of

friends)

Polyatomic con’t

You need to learn their namesJust use their names (no prefixes or

suffixes)Fewer oxygens have –iteMore oxygens have –ateNH4OH is ammonium hydroxide

Molecules

Nonmetals form molecules with each other They share electrons They may form more than one compound with

each other Use prefixes to tell how many of each element

Prefixes and meanings

Mono = 1

Di = 2

Tri = 3

Tetra = 4

Penta = 5

Hexa = 6

Hepta = 7

Octa = 8

Nona = 9

Deca = 10

Use of prefixes

The least electronegative element is written first – use the name of this element

The second element is named using the –ide ending

Use prefixes to show how many of each element

Do not use –mono if there is only one of the first element

Molecule examples

CO is carbon monoxide

CO2 is carbon dioxide

Note: since there is only one carbon, no prefix is used

N2H4 is dinitrogen tetrahydride

Hydrates

These prefixes can also be used for hydrates(compounds that contain water molecules)

Example CuSO4 . 5 H2O is :

copper II sulfate penta hydrate

Naming Acids

Acids are compounds that give off H+ ions in solution (aq)

Binary Acids

Hydrogen and one nonmetal Basic formula of HX Add –hydro as a prefix Add – ic as a suffix Example: hydrogen and chloride ion HCl is named hydrochloric acid

Acids with polyatomic anions

The –ate ending becomes –ic

Example: NO3- is nitrate ion

Combined with hydrogen ion in solution it becomes HNO3

This compound is named nitric acid

Polyatomic (oxyacids) con’t

The –ite ending becomes –ous

NO2- is nitrite ion

It forms nitrous acid which is written HNO2

Acids to Know

HCl

H2SO4

HNO3

HC2H3O2

H3PO4

H2CO3

Chapter 5 Review Problems

P. 137

# 47 Write the formulas

a. Lithium hydrogen sulfate

b. Chromium III nitrite

c. Mercury II bromide

d. Ammonium dichromate

a. LiHSO4

b. Cr(NO2)3

c. HgBr2

d. (NH4)2Cr2O7

50. Name the binary molecules

a. OF2

b. Cl2O8

c. SO3

d. P4O10

a. Oxygen difluoride

b. Dichlorine octoxide

c. Sulfur trioxide

d. Tetraphosphorus decoxide

51. Write formulas for binary molecules.

a. Nitrogen trifluoride

b. Disulfur dichloride

c. Dinitrogen tetroxide

d. Phosphorus pentachloride

a. NF3

b. S2Cl2

c. N2O4

d. PCl5

52. Give the name or formula for these acids.

a. HCl

b. HNO3

c. Sulfuric acid

d. Acetic acid

Hydrochloric acid

Nitric acid

H2SO4

HC2H3O2

56. Write the formulas

a. Potassium permanganate

b. Calcium hydrogen carbonate

c. Dichlorine heptoxided. Trisilicon tetranitridee. Skipf. Phosphorus

pentabromideg. Carbon tetrachloride

a. KMnO4

b. Ca(HCO3)2

c. Cl2O7

d. Si3N4

e. NaH2PO4

f. PBr5

g. CCl4