Chapter 9 Chemical Names and Formulas

9.1 - Naming Ions

Monatomic ions: Single atom with a positive or negative charge resulting from the loss or gain of one or more valence electrons.

- Cations: Groups 1A, 2A and 3A (+ charge)

- Anions: Groups 5A, 6A and 7A (- charge)

● The charges of the cations of many transition metal ions must be determined from the number of electrons lost.○ Example: Fe2+ and Fe3+

* Note: Know the stock name, but we will be using the classical name sometimes during labs.

Polyatomic Ions: Composed of more than one atom.

● The names of most polyatomic anions end in -ite or -ate.

● -ite: indicates one less oxygen atom

● -ate: indicates one more oxygen atom than -ite.

Examples: Chlorate (ClO3-) vs.

Chlorite (ClO2-), Sulfate (SO4

2-) vs. Sulfite (SO3

2-)

Naming: When it begins with hydrogen or any other element, Say the name of the first element and add the proper ending to the last element in the formula.

Example: H+ + CO32- -> HCO3

-

- Hydrogen Carbonate

b) H+ +PO43- -> HPO4

2-

- Hydrogen Phosphate

c) Formula: K2CO3 = ??

9.2 - Naming and Writing Formulas for Ionic Compounds

Binary Compounds: Composed of two elements and can be either ionic or molecular.

- To name any binary ionic compound, place the cation name first, followed by the anion name.

Example: NaBr - Sodium Bromide

b) Cs2O - Cesium Oxide

Formulas: Write the symbol of the cation and then the anion. Add whatever subscripts are needed to balance the charges.

Ex: KCl - Potassium Chloride

b) Fe3+ + O2- = Iron (III) Oxide

- What is the formula?

c) Calcium Sulfide Formula?

Formulas for Compounds with Polyatomic Ions: Write the symbol for the cation followed by the formula for the polyatomic ion and balance the charges.

a) Calcium Nitrate: Ca2+ + NO3-

Answer: ???

b) Lithium Carbonate: Li? + CO32-

Answer: ???

Naming Compounds with Polyatomic Ions: State the cation first and then the anion.

- Same as Binary Ionic Compounds

9.3 - Naming and Writing Formulas for Molecular Compounds

● A prefix in the name of a binary molecular compound tells how many atoms of an element are present in each molecule of the compound.

● When naming the compounds say the name of the first element.

Example: CO2 - Carbon Dioxide

● Cl2O8 - ???

● Use the prefixes in the name to tell you the subscript of each element in the formula. Then write the correct symbols for the two elements with the appropriate subscripts.

● Ending is -ide

9.4 - Naming and Writing Formulas for Acids and Bases

Acid: a compound that contains one or more hydrogen atoms and produces hydrogen ions. (H+)

Rules:

1) When the name of the anion ends in -ide, the acid name begins with the hydro-, The stem of the anion has the suffix -ic and is followed by the word acid. (HCl - Hydrochloric Acid)

2) When the anion ends in -ite, the acid name is the stem of the anion with the suffix -ic followed by the word acid. (H2SO3 - Sulfurous Acid)

3) When the anion name ends in -ate, the acid name is the stem of the anion with the suffix -ic followed by the word acid. (HNO3) Nitric Acid

Formulas: Use the rules for writing names of acids in reverse to write the formulas for acids.

- Hydrobromic Acid: HBr- Phosphoric Acid: ???- Carbonic Acid: ???

Base: an ionic compound that produces hydroxide ions when dissolved in Water.

- Bases are names in the same way as other ionic compounds - the name of the cation is followed by the name of the anion.

Example: NaOH - Sodium Hydroxide

9.5 - The Laws Governing Formulas and Names

Law of Definite Proportions: In samples of any chemical compound, the masses of the elements are always in the same proportions. (atoms combine in whole number ratios)

Ex: H2O - 2:16

Law of Multiple Proportions: Whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other element in the ratio of the small whole numbers.

- Work in ratios

Writing Chemical Formulas:

1) An -ide ending generally indicates a binary compound.

2) An -ite or -ate ending means a polyatomic ion that includes oxygen is in the formula.

3) Prefixes in a names generally indicate that the compound is molecular.

4) A Roman numeral after the name of the cation shows the ionic charge of the cation.

To calculate the percent composition of a component in a compound:1. Find the molar mass of the compound by

adding up the masses of each atom

2. in the compound using the periodic table or a molecular mass calculator. Calculate the mass due to the component in the compound you are for which

3. you are solving by adding up the mass of these atoms. Divide the mass due to the component by the total molar mass of the compound,and multiply by 100.

Mole: Particle of a substance

Solving for moles:

moles = mass ÷ molar mass