4

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A. Definition

•Remember, a compound consists of 2 or more elements chemically bonded together. It is always neutral.

EX: H2O, NaCl, Sb3(PO4)5

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•There are two main ways to name chemical compounds. However, before you can even think about naming the compound you must decide what kind of compound you have. Do you have a covalent or ionic compound? We already learned this using the terms molecule and formula unit.

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•Most formulas are written with the elements listed from left to right on the periodic table

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What do you remember about the difference between a molecule and a formula unit?

B. Types of Compounds

2 types of chemical compounds

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SamplesIonic

Compounds• Rock salt (NaCl)• Calcium Carbonate

(CaCO3)

• Potassium Nitrate (KNO3 )

Molecular Compounds

• Sugar (C12H22O11)

• Methane gas (CH4)

What’s the difference?

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1. Ionic Compound:Ionic Compound: a compound that is

formed by ions of opposite charges. It is held together by an ionic (transfer electrons) bond and usually contains a metal and nonmetal.

EX: NaCl, Sb3(PO4)5

smallest unit is called a formula unit

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2. Molecular or Covalent Compound:

• Molecular or Covalent compound: consists of only nonmetal atoms and is held together by covalent (share electrons) bonds

EX: H2O, C8H18

smallest unit is called a molecule

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How can I tell!?

•Look for a metal.

•If there’s a metal, it’s an ionic compound

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Practice1. Determine whether the

following are ionic or molecular covalent compounds

a. N2O5 b. PbNO5

c. KF d. AgCl

e. PCl3

ionic

molecular

molecular

ionic

ionic

KF AgCl

PbNO5

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Acids: have a formula that starts with hydrogen

You need to know the names and formulas for the following acids:

Acid Name Formula

hydrochloric acid HCl

nitric acid HNO3

sulfuric acid H2SO4

phosphoric acid H3PO4

Note: all acids start with “H” in their chemical formulas and include the word

“acid” in their names.

II. Molecular Compounds

(aka Covalent Compounds aka

Molecules)

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Molecular Compounds = share electrons

H O

H2OH

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A. Binary Molecular Compounds

•Molecular compounds DO NOT contain a metal atom

•Molecular compound contain covalent bonds

•We use prefixes to name molecular, ONLY MOLECULAR, compounds

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How do I distinguish between the bikes?

unicycle bicycle tricycle

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We use prefixes to help distinguish molecular

compounds.Prefix Number of Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

hepta 7

octa 8

nona 9

deca 10

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Why have prefixes?Nitrogen bonds to Oxygen

in more than one way

Ex: N2O, NO2, N2O2, N2O5

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Examples:Formula: CO

Name:

Formula: N2O

Name:

carbon monoxide

dinitrogen monoxide

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a. Naming binary molecular compounds:

FIRST ELEMENT IN THE FORMULA – keeps its full elemental name – Add prefixes to signify the number of

that specific kind of atom ONLY if there is more than one of the atoms. DON’T USE MONO ON THE FIRST SYMBOL

SECOND ELEMENT IN THE FORMULA– The second element name ALWAYS

gets a prefix– Keep the first syllable of the

elemental name and change the suffix to “ide”.

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Practice:Formula: CO2 name:Formula: BF3 name:Formula: Cl2O name:Formula: P2S5 name:

Carbon dioxide

Boron trifluorideDichlorine monoxideDiphosphorus pentasulfide

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B. Converting a name to a formula:

•This exercise is very simple if you have memorized the element symbols and the prefixes. Just go backwards from what we just did.

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Examples:Formula: Name: carbon tetrachloride.

Formula: Name: dihydrogen monofluoride

CCl4

H2F

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Practice:Formula: H2O name: Dihydrogen monoxideFormula: name: Nitrogen pentoxide Formula: name: CarbonTetrafluoride Formula: name: Silicon Dioxide

NO5

CF4

SiO2

1+

2+ 3+ 3- 2- 1-

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III. Naming ions1. Monatomic Cations (+ ions)

•Monatomic cations are named by writing the element’s name and then “ion” after it.

•EX: Ca2+ Na+

One atom +

Sodium ion

Calcium ion

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a. Monatomic Cations (Transition + PASS + Z.A.C

Elements )• Most transition metals and “P.A.S.S” elements need Roman Numerals

• Zinc (Zn), Silver (Ag), and Cadmium (Cd) are transition metals that DO NOT need Roman Numerals “Z.A.C Elements”

• Roman Numerals 1-5: I, II, III, IV, V

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More than just “Iron ion”

EX: Fe2+ Fe3+

Iron (III) ionIron (II) ion

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Transition Metals need R.N.1. Name these

ionsa. Pb4+ b. Pb2+

c. Cu+ d. Cu2+

Lead (IV) ionLead (II) ionCopper (I) ionCopper (II) ion

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Examples1. Name these ionsa. Ca2+ b. Na+

c. Fe4+ d. Zn2+

Calcium ionSodium ionIron (IV) ionZinc ion

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b. Monoatomic Anions (- ions)

oMonatomic anions are named by changing the suffix to “ide” then adding “ion” after it.

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Cation or Anion?• Carbon can act as a cation (carbon

ion) or as an anion (carbide ion). It just depends if it is in the beginning or the end of the compound’s formula

• Hydrogen can also act as a cation (hydrogen) or as an anion (hydride). It just depends if it is in the beginning or the end of the compound’s formula. Don’t forget it is a non-metal.

Complete the chart below

Element SymbolOxidation number

Anion name

Chlorine Cl- -1 Chloride ion

Bromine Br- -1 Bromide ion

Oxygen

S2-

Phosphide ion

N3-

Sulfur

O2- -2 Oxide ion

-2 Sulfide ion

Phosphorus P3- -3

Nitrogen -3 Nitride ion

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Summary•List the elements that need Roman Numerals

•List the transition metals that don’t need Roman Numerals

Transition metals, PASS elements (Pb, As, Sn, Sb)

Zn, Ag, Cd (Z.A.C elements)

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Always need roman numerals

1+

2+ 3+ 3- 2- 1-

TipsTM (Except ZAC) and PASS need Roman NumeralsAll metals are +; all non-metals are -Anions end in -ide

Anions: Change Suffix to -ide

Zn2+ Cd2+Ag+

always

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c. Polyatomic Cations

•A polyatomic ion is a group of covalently bonded atoms that have an overall charge

•Example NH4

+ = ammonium.

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d. Polyatomic Anions • This means the anion is a

COVALENTLY BONDED GROUP of atoms that have a – charge. They are EASY to deal with in naming and formula writing if you think of them as ONE UNIT that can not be altered in any way.

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Example:

•Use the back of your periodic table to help you identify polyatomic anions

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Flip over your PT and let’s practice

1. Name these ionsa. CO3

2- b. OH- c. NO3

- d. SO4

2-

e. PO43-

carbonatehydroxidenitratesulfatephosphate

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IV. Binary Ionic Compoundsa. Naming Binary Ionic Compounds

• Ionic Compounds are made of a cation and anion pair. You already know how to name the ions. Just put the names together and leave off the word ion. Don’t forget Roman Numerals!

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Ionic Compounds = transfer of electrons

Na Cl+ -

NaClIs formed

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a. Naming Binary Ionic Compounds

Formula

Ions Ion names Compound name

AlNAl3+

N3- Aluminum ionNitride ion

Na20Na+

O2-

Sodium ionOxide ion

FeOFe2+

O2-

Fe2O3Fe3+

O2-

Iron (II) ionOxide ion

Iron (III) ionOxide ion

Aluminum nitride

Sodium oxide

Iron (II) oxide

Iron (III) oxide

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Ex. Name FeS

Iron Sulfide

Iron (II) sulfide

NOT

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Remember to add a Roman Numeral for the cations that need one

One trick to determine the Roman Numeral:1. Add up your total negative

charges2. Divide the above number by the

total number of metal ions3. Change to a Roman

Numeral

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Ex. Name FeS

Total neg. charges: 2-2/1 (Fe) = 2

1. Add up your total negative charges2. Divide the above number by the

total number of metal ions3. Change to a Roman

Numeral

Iron (II) Sulfide

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Ex. Name Fe2O3

Total neg. charges: 6-6/2 (Fe) = 3

Iron (III) Oxide

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Practice

1. Name the following compounds

a. ZnS

b. K3N

c. BaO

d. CaBr2

e. SnF2

Zinc sulfide

Potassium nitride

Barium oxide

Calcium bromide

Tin (II) fluoride

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Practice

1. Name the following compounds

f. CaO

g. AlF3

h. CuI2

i. Cu2Se

j. Hg2O

Calcium oxide

Aluminum fluoride

Copper (II) iodide

Copper (I) SelenideMercury (I) Oxide

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b. Writing Formulas for Binary Ionic Compounds

•Remember, a compound must be electrically neutral. Therefore, the total positive charge of the cation must equal the total negative charge of the anion.

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EX: calcium chloride

Ca2+ Cl-

To make a neutral compound Ca2+ Cl-

Cl-+2 -2

CaCl2

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To write a formula for a binary ionic compound1.Write the ions that are named in the compound showing oxidation numbers.2. Determine how many of each ion you need to make a neutral compound.3. To write the formula, list the metal symbol first and then the anion symbol, adding subscripts to indicate how many of each ion there is in the formula4. Make sure the formula has the lowest whole number ratio.

Note: you never write a 1 subscript; it is understood.

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EX: write the formula for aluminum fluoride

Al+3 F-

NOTE: You never include oxidation numbers in the chemical formula of a compound.

Formula: AlF3

F-

F-

+3 -3

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Practice – only do a-c1. Write chemical formulas for the following:

a. strontium phosphide

b. potassium sulfide

c. iron (II) chloride

Sr3P2

K2S

FeCl2

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The Criss-Cross Method

•One easy way to figure out the formula of an ionic compound is to swap the oxidation number of each ion and use them as subscripts. (without the charge)

•the formula must be in the lowest whole number ratio

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Na S

Just Watch!!

sodium sulfide

1 2+ -

1’s are understood

Na2S

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Fe Br

Ex: Write the formula for iron (III) bromide

3+ -

FeBr3

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Mg S

Ex: Write the formula for magnesium sulfide

2 2+ -

Note: if both ox #’s are equal, you don’t need to use the

crisscross method, just show 1 ion of each.

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Magnesium Sulfide

MgS(not Mg2S2)

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Pb S

Note: show the formula with the lowest whole number ratio.

EX: write the formula for lead (IV) sulfide

4 2+ -

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Criss Cross Method

Pb2S4

PbS2

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Finish the Practice Box1. Write chemical formulas for the following:

d. antimony (V) nitride

e. iron (III) chloride

f. Calcium bromideCaBr2

FeCl3

Sb3N5

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Naming

•Same way as you already learned

•Use subscripts to show how many of each ion you needed to make a neutral compound

Formulas

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V. Ionic Compounds Containing Polyatomic

Ions a. Writing Formulas for Polyatomic Compounds

• Write formulas for polyatomic ions in the same way. Just remember the polyatomic ion acts as a whole unit and you need to use parentheses if you need more than 1 of them.

• Note: You never change the • formula of a polyatomic ion!

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EX: calcium nitrate

To make a neutral compound Ca2+

(NO3)-

(NO3)-

+2 -2Ca(NO3)2

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Ca (NO3)

EX: Calcium Nitrate(using the criss cross

method)

2+ -

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PracticePractice1. Write formulas for the following

compoundsa. strontium sulfate

b. lithium carbonate

c. potassium sulfate

d. magnesium hydroxide

SrSO4 or Sr(SO4)

Li2CO3 or Li2(CO3)

Mg(OH)2

K2SO4 or K2(SO4)

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PracticePractice1. Write formulas for the following

compoundse. ammonium dichromate

f. potassium permanganate

g. sodium hypochlorite

h. barium sulfite

(NH4)2Cr2O7 or (NH4)2(Cr2O7)

NaClO or Na(ClO)

BaSO3 or Ba(SO3)

KMnO4 or K(MnO4)

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b. Naming Polyatomic Compounds

•It is important that you recognize the polyatomic

• If there are more than 2 elements in the formula, then you know it contains a polyatomic.

•Only one polyatomic is a cation, ammonium (NH4

+) All the rest will come after the metal ion.

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•You name polyatomic compounds just like you would other ionic compounds -- you write the name of each ion. Note: most (not all) polyatomic compounds will end in -ate or -ite.

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Ex. Name ZnSO4

Zinc

Ex. Name NaOH

Sodium

Sulfate

hydroxide

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Practice1. Name these compoundsa. CaCO3

b. KClO

c. KMnO4

calcium carbonate

potassium hypochlorite

potassium permanganate

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Practice1. Name these compounds

d. Al(OH)3

e. Sn3(PO4)2

f. Na2CrO4

aluminum hydroxide

tin (II) phosphate

sodium chromate