Chapter 9 chemical names and formulas

Chapter 9 chemical names and formulas

Calcium Carbonate

Carbon Dioxide

Dinitrogen MonoxideStrontium Sulfate

Hydrogen Phosphate

Potassium Sulfate

Naming IonsMonatomic Ions

Single atom with a positive or negative charge

i. Cation1. Lose electrons

2. Positive charge

3. Name remains the sameNa is SodiumNa+ is Sodium cation

ii. Anion

1. Gain electrons

2. Negative charge3. Name starts with the stem and ends in -ide

N is Nitrogen

N3- is Nitride

iii. Transition Metals

1. Lose electrons - cations

2. Positive charge

4. Two ways to name them

3. Transition metals may lose a different number of electrons creating ions with a different charge

a. Stock system-most common way of namingi. A roman numeral is

placed next (with no spaces) to the name of the element indicating the charge

Fe2+ is Iron(II) ion

Fe3+ is Iron(III) ion

Co2+ is Cobalt(II) ionCo3+ is Cobalt(III) ion

b. Classic system-older, less useful way

i. Root word with –ous at the end of the ion with the smaller charge and –ic at the end of the ion with the larger charge

Fe2+ is Ferrous ion

Fe3+ is Ferric ion

Co2+ is Cobaltous ionCo3+ is Cobaltic ion

**There are special metals that change their charge – Tin (Sn) and Lead (Pb)

FYI – many of these transition metal cations are colored and are used as pigments which are used to make different colored paints

Polyatomic IonsIons composed of more than one atom

i. Most that end in -ite or -ate contain Oxygen

iii. The names need to be memorized

ii. If the formula begins with H then the name usually begins with Hydrogen

Naming Ionic CompoundsCompound Names

i. Names of compounds used to be determined by the person who discovered it and the name related to the compounds property or what it was used for

NaHCO3 baking soda – used to bake cakesCaSO4 + ½H2O plaster of Paris – used to make plaster faces

Make it easier to identify names

ii. As more compounds were discovered, it became harder to memorize all the unrelated names.

iii. Antione Lavoisier worked with other chemists to devise a naming system

Binary Ionic Compoundsi. Binary CompoundsIonic or molecular compounds

composed of two elements

ii. Binary Ionic Compounds

Ionic compound composed of a cation and an anion

Naming Binary Ionic Compoundsi. Name the cation first

ii. Name the anion second

Examples: Catio

nAnion Ionic

CompoundCs2O Cesium

Oxide Cesium Oxide

NaCl Sodium

Chloride

Sodium ChlorideSrF2 Strontiu

m Fluoride Strontium

FluorideSnF2

SnS2

Remember Tin is a special metal and needs roman numerals

* *

Cation

Anion Ionic Compound

SnF2 Tin(II) Fluoride Tin(II) Fluoride

SnS2 Tin(IV) Sulfide Tin(IV) Sulfide

Writing Formulas for Binary Ionic Compounds

ii. Write the symbol of the cation and charge

i. If you know the name of the Ionic Compound you can write the formula

iii. Write the symbol of the anion and charge

iv. Add the required subscripts (the positive and negative charges must balance

Examples: Catio

nAnion Ionic

CompoundPotassium Chloride

K+ Cl- KCl

Calcium Bromide Ca2+ Br- CaBr2

Iron(III) Oxide Fe3+ O2- Fe2O3

Naming compounds with polyatomic ions

i. Name the cationsii. Name the polyatomic anionExamples:

Cation

Polyatomic ion Compound

CaCO3

Calcium

Carbonate

Calcium Carbonate

K2HPO4 Potassium

Hydrogen Phosphate

Potassium Hydrogen Phosphate

K2SO4 Potassium

Sulfate Potassium Sulfate

Writing formulas for compounds with polyatomic ions

i. If you know the name of a compound you can write the formula

ii. Write the symbol of the cation and the charge

iii. Write the symbol of the polyatomic anion and the charge

iv. Add the required subscripts (positive and negative charges must balance)

Examples:

Cation

Polyatomic ionCompoundCalcium

Nitrate Ca2

+

NO3- Ca(NO3)

2

Strontium Sulfate

Sr2+ SO42- SrSO4

Naming Molecular CompoundsBinary Molecular compounds

Two elements covalently bonded

Naming Binary Molecular compoundsi. A prefix is added to an element

to state how many of each atom is present (prefix is always added to the second element and only added to the first if the number is greater than one)

Mono Di Tri Tetra Penta Hexa Hepta Octa Nona Deca

1 2 3 4 5 6 7 8 9 10

Examples:

ii. -ide is added to the end of the second molecule

CO Carbon

Monoxide

CO2

Dinitrogen

Dioxide

N2O

Carbon

Monoxide

Cl2O8 Dichlorine

Octoxide

Writing formulas for Molecular Compounds

i. Write the symbol for the first nonmetal

ii. Write the symbol for the second nonmetal

iii. Use the prefixes to tell you the subscripts

Examples:First Second Formula

Silicon Monocarbide

Si C SiC

Phosphorus pentachloride P Cl5 PCl5

Chlorine trifluoride

Cl F3 ClF3

Dinitrogen tetroxide

N2 O4N2O4

AcidsAcids

- Group of ionic compounds that contains one or more hydrogen atoms and produces hydrogen ions (H+) when dissolved in water.

Naming Acids

1. When anion ends in –ide the acid name begins with the prefix hydro-, the stem of the anion with the suffix –ic followed by acid

Three Rules

Example:

HCl

* Anion is Chloride

* Name begins with hydro

hydro

* Then the stem of the anion -chlor

chlor

* Then the suffix -ic

ic

* Followed by Acid

acid

2. When anion ends in –ite, the acid name is the stem of the anion with the suffix –ous followed by the word acidExample:

H2SO3

* Anion is Sulfite (pg 257)* Name begins with stem of anion Sulfur

sulfur

* Then the suffix -ous

ous

* Followed by Acid

acid

3. When anion ends in –ate, the acid name is the stem of the anion with the suffix –ic followed by the word acidExample:

HNO3

* Anion is Nitrate (pg 257)

* Name begins with stem of anion Nitr

nitr

* Then the suffix -ic

ic

* Followed by Acid

acid

Writing formulas for Acids

i. The general formula for acids is HnX

where X is the monatomic or polyatomic anion and n is a subscript for the number of hydrogen atoms needed to make the compound neutral

ii. Use the three rules for naming acids in reverse and then balance

Example:

Hydrobromic acid

* Hydro and -ic --- anion ends in -ide

Br-

* Followed by Acid --- Formula is HnX

H+

* Balance

HBr

Phosphorous acid

* Followed by Acid --- Formula is HnX

H+

* -ous --- anion ends in –ite (pg 257)

PO33-

* Balance

H3PO3

Sulfuric acid

* Followed by Acid --- Formula is HnX

H+

* -ic --- anion ends in –ate (pg 257)

SO42-

* Balance

H2SO4

Names and formulas for Basesbases

- Ionic compound that produces hydroxide ion (OH-) when dissolved in water

Naming

i. Name the cation

ii. Name the anion (hydroxide)

Examples:

NaOH

* Name the cation - Sodium

* Name the anion - HydroxideSodium Hydroxide

Al(OH)3

Aluminum Hydroxide

Writing formulas for bases

i. Write the symbol for the cation and charge

ii. Write the symbol for the anion and charge (OH-)

iii. Balance the formula (positive and negative charges must balance)

Examples:

Potassium hydroxide

* Anion and charge – OH-

* Cation and charge – K+

K+ OH-

KOH

* Balance

Laws governing Formulas and Names

Naming using these methods is possible because elements form compounds in

predictable ways

Laws of Definite Proportions

In samples of any chemical compound, the masses of the elements are always in the same proportions because atoms combine in simple whole number ratios

Laws of Multiple Proportions

Whenever the same two elements form more than one compound, the different masses of one element that combine with the same masses of the other elements are in the ratio of small whole numbers