IONIC COMPOUNDSIONIC COMPOUNDS

Ionic Compounds:Ionic Compounds:

Form when metals and nonmetals combine by transferring electrons

Metal atoms lose electrons to form positive ions

Nonmetal atoms gain electrons to form negative ions

Electrons are transferred from metal to nonmetal, and the resulting charged particles (ions) form an IONIC BOND

Ionic ChargesIonic Charges

Determined by the number of electrons in the outermost “shell” – VALENCE

Eg. Aluminum: Al has 13 protons, 13 electrons (2 in first shell, 8 in second, 3 in third)

Al will lose the 3 electrons in the outermost shell and therefore has a valence of 3

Formulas for Ionic Formulas for Ionic Compounds:Compounds:

Eg. Calcium iodide Write the symbols for elements: Ca IWrite the ionic charges: Ca 2+ I 1-Select the number of ions to balance the

charge CaI2

Criss-Cross RuleCriss-Cross Rule

Calcium IodideCalcium Iodide

2+ 1-2+ 1-

Ca ICa I

Nickel and OxygenNickel and Oxygen

Write chemical symbols: Ni ODetermine valence or ionic charges Ni2+

O2- Use criss cross rule: 2+ 2-

Ni O Write formula: Ni2O2

Reduce formula: NiO

POLYATOMIC COMPOUNDSPOLYATOMIC COMPOUNDS

Pure substances involving combinations of metals and polyatomic ions

POLYATOMIC IONS are groups of atoms that tend to stay together and carry an overall ionic charge

Eg. Nitrate NO3-

Eg. Sulfate SO42-

Formulas for polyatomic Formulas for polyatomic compounds:compounds:

Eg. What is the formula for the ionic compound formed by sodium and a hydroxide ion?

WRITE THE SYMBOLS FOR THE IONS: Na OH

WRITE THE CHARGES ABOVE EACH: 1+1-

Na OH CRISS CROSS CHARGES AND SYMBOLS WRITE THE FORMULA: NaOH

Naming polyatomic Naming polyatomic compounds:compounds:

Combination of the metal and the name of the polyatomic ion

Eg. NaOH sodium hydroxide

Determine the formula and Determine the formula and name the compound formed name the compound formed by combining calcium and by combining calcium and

carbonate ion.carbonate ion.

2+2+ 2-2-

CaCa COCO33--

CaCOCaCO33

Calcium carbonateCalcium carbonate

MOLECULAR COMPOUNDSMOLECULAR COMPOUNDS

Most of the compounds you encounter everyday do not contain ions. Instead they contain molecules which share electrons to form stable arrangements.

This sharing of electrons is called a covalent bond.

Many nonmetals form covalent bonds.

Diatomic MoleculesDiatomic Molecules

Certain elements such as oxygen exist as covelently bonded molecules.

The table on p. 202 of your text lists the elements that form diatomic molecules. Copy the information into your notes.

Prefixes in Molecular CompoundsPrefixes in Molecular Compounds

Prefix Number Example

mon(o)- 1 CO

di- 2 CS2

tri- 3 SO3

tetra- 4 CF4

pent(a)- 5 PBr5

Formulas for molecular compounds:Formulas for molecular compounds:

• E.g. What is the formula for a compound formed between carbon and sulfur?

• Write the symbols and their combining capacities. Write the one with the larger combining capacity first:

4 2C S

• Criss cross combining capacities to produce subscripts:

C2S4

• Reduce the subscripts if possible: CS2

Naming Molecular Compounds:Naming Molecular Compounds: Molecular compounds containing hydrogen are named

as if they were ionic compounds.

eg. H2S hydrogen sulfide Others have common names such as water (H2O),

ammonia (NH3), or methane (CH4). In general, prefixes are used to count the number of

atoms when the same two elements form different combinations.

IF there is only one atom of the first element, the prefix “mono” is not used.

eg. CO Carbon monoxide

eg. CO2 Carbon dioxide