Classifying Materials

Classifying Materials

• Atomic elements = elements whose particles are single atoms.

• Molecular elements = elements whose particles are multi-atom molecules.

• Molecular compounds = compounds whose particles are molecules made of only nonmetals.

• Ionic compounds = compounds whose particles are cations and anions.

Molecular View of Elements and Compounds

Molecular Elements

• Certain elements occur as 2 atom molecules• Rule of 7’s

– there are 7 common diatomic elements– find the element with atomic number 7, N– make a figure 7 by going over to Group 7A, then down– don’t forget to include H2

H2

Cl2

Br2

I2

7VIIA

N2 O2 F2

Ionic Compounds

• Ionic compounds form when metals combine with nonmetals.

• There are no individual molecules, instead there is a 3-dimensional array made up of formula units of cations and anions.

• metal atoms form cations, nonmetal atoms for anions

• Compounds must have no total charge, therefore we must balance the numbers of cations and anions in a compound to get 0 charge

• If Na+ is combined with S2-, you will need 2 Na+ ions for every S2- ion to balance the charges, therefore the formula must be Na2S

Molecular Compounds

• two or more nonmetals

• smallest unit is a molecule

Classify each of the following as either an atomic element, molecular element, molecular compound

or ionic compound

• aluminum, Al

• aluminum chloride, AlCl3

• chlorine, Cl2

• acetone, C3H6O

• carbon monoxide, CO

• cobalt, Co

Classify each of the following as either an atomic element, molecular element, molecular compound

or ionic compound

• aluminum, Al = atomic element

• aluminum chloride, AlCl3 = ionic compound

• chlorine, Cl2 = molecular element

• acetone, C3H6O = molecular compound

• carbon monoxide, CO = molecular compound

• cobalt, Co = atomic element

Metal Cations

• Type I

– metals whose ions can only have one possible charge

• IA, IIA, (Al, Ga, In)

– determine charge by position on the Periodic Table

• IA = +1, IIA = +2, (Al, Ga, In = +3)

• Type II

– metals whose ions can have more than one possible charge

– determine charge by charge on anion

How do you know a metal cation is Type II?

It’s not Type I !!!

Determine if the following metals are Type I or Type II. If Type I, determine the charge on the cation it

forms.

• lithium, Li

• copper, Cu

• gallium, Ga

• tin, Sn

• strontium, Sr

Determine if the following metals are Type I or Type II. If Type I, determine the charge on the cation it

forms.

• lithium, Li Type I +1

• copper, Cu Type II

• gallium, Ga Type I +3

• tin, Sn Type II

• strontium, Sr Type I +2

Type I Binary Ionic Compounds

• Contain a Metal Cation + a Nonmetal Anion

• Common simple cations and anions are listed in Table 5.1

• The Metal is listed first in the formula & name

1. Name the metal cation first, name the nonmetal anion second.

2. The cation name is the same as the metal name.

3. The nonmetal anion is named by changing the ending on the nonmetal name to –ide

Example – Naming Binary Ionic, Type I Metal CsF

1. Identify Major Class Cs = is a metal because it is on the left side of the Periodic TableF = is a nonmetal because it is on the right side of the Periodic Table: Ionic

2. Identify the Subclass

2 elements: Binary Ionic

3. Is the metal Type I or Type II?

Cs is in Group IA: Type I4. Identify the cation and anion

Cs = Cs+ because it is in Group 1F = F- because it is in Group 7

5. Name the cationCs+ = cesium

6. Name the anionF- = fluoride

7. Write the cation name first, then the anion namecesium fluoride

Type II Binary Ionic Compounds• Contain a Metal Cation + a Nonmetal Anion

• Metal ions are listed first in the formula & name

1. Name the metal cation first, name the nonmetal anion second.

2. Metal cation names are the metal name followed by a Roman Numeral in parentheses to indicate the charge on the cation.

– determine charge from the anion charge

– Common Type II cations (elements that have more than one possible charge) are listed in Table 5.2

3. Nonmetal anions are named by changing the ending on the nonmetal name to -ide

Example – Naming Binary Ionic, Type II MetalCuCl

1. Identify Major ClassCu = is a metal because it is on the left side of the PTCl = is a nonmetal because it is on the right side of the PT

Ionic2. Identify the Subclass

2 elements, Binary Ionic3. Is the metal Type I or Type II

Cu is not in Group IA, IIA, or (Al, Ga, In) Type II4. Identify cation and anion

Cl = Cl- because it is Group 7Cu = Cu+ to balance the charge

5. Name the cationCu+ = copper(I)

6. Name the anionCl- = chloride

7. Write the cation name first, then the anion namecopper(I) chloride

Determining the Charge on a Multivalent Cation – Au2S3

1. determine the charge on the anion

Au2S3 - the anion is S, since it is in Group 6A, its charge is -2

2. determine the total negative chargesince there are 3 S in the formula, the total negative charge is -6

3. determine the total positive chargesince the total negative charge is -6, the total positive charge is +6

4. divide by the number of cationssince there are 2 Au in the formula & the total positive charge is +6, each Au has a +3 charge

Examples: Name the following

• LiCl

• AlCl3

• PbO

• PbO2

• Mn2O3

• ZnCl2

• AgCl

Examples

• LiCl = lithium chloride

• AlCl3 = aluminum chloride

• PbO = lead(II) oxide

• PbO2 = lead(IV) oxide

• Mn2O3 = manganese(III) oxide

• ZnCl2 = zinc(II) chloride or zinc chloride

• AgCl = silver(I) chloride or silver chloride

Naming Type III Binary Molecular Compounds of 2 Nonmetals

1. Name the first element in the formula first

– use the full name of the element

2. Name the second element in the formula with an -ide

– as if it were an anion, however, remember these compounds do not contain ions!

3. Use a prefix in front of each name to indicate the number of atoms

Never use the prefix mono- on the first element

Subscript - Prefixes

• 1 = mono-– not used on first nonmetal

• 2 = di-• 3 = tri-• 4 = tetra-• 5 = penta-• 6 = hexa-• 7 = hepta-• 8 = octa-• drop the last “a” if the name begins with a vowel

Remember these prefixes listed in Table 5.3

Example – Naming Binary MolecularBF3

1. Identify Major Class

B = is a nonmetal because it is on the right side of the PT

F = is a nonmetal because it is on the right side of the PT

Molecular

2. Identify the Subclass

2 elements: Binary Molecular4. Name the first element

boron5. Name the second element with an –ide

fluorine fluoride6. Add a prefix to each name to indicate the subscript

monoboron, trifluoride7. Write the first element with prefix, then the second element with prefix

– Drop prefix mono from first elementboron trifluoride

Compounds Containing Polyatomic Ions

• Polyatomic ions are single ions that contain more than one atom.

• Name these compounds using procedures similar to those for naming binary ionic compounds.

• Use Table 5.4 to help you recognize these ions until you have memorized them.

• Note that several polyatomic anions exist that contain an atom of a given element and different numbers of oxygen atoms. These anions are called oxyanions. E.g. oxyanions containing chlorine are:

• ClO- hypochlorite

• ClO2- chlorite

• ClO3- chlorate

• ClO4- perchlorate

Some Common Polyatomic Ions

Name Formula

acetate C2H3O2–

carbonate CO32–

hydrogen carbonate(bicarbonate)

HCO3–

hydroxide OH–

nitrate NO3–

nitrite NO2–

chromate CrO42–

dichromate Cr2O72–

ammonium NH4+

Name Formula

hypochlorite ClO–

chlorite ClO2–

chlorate ClO3–

perchlorate ClO4–

sulfate SO42–

sulfite SO32–

Hydrogen sulfate(bisulfate)

HSO4–

Hydrogen sulfite(bisulfite)

HSO3–

Molecules with Polyatomic Ions

Mg(NO3)2

compound calledmagnesium nitrate

symbol of the polyatomic ion called nitrate

symbol of the polyatomic ion called sulfate

CaSO4

compound calledcalcium sulfate

implied “1” subscripton magnesium

implied “1” subscripton calcium

parentheses to group two NO3’s no parentheses for one SO4

Molecules with Polyatomic Ions

Mg(NO3)2

compound calledmagnesium nitrate

CaSO4

compound calledcalcium sulfate

subscript indicatingtwo NO3 groups

no subscript indicatingone SO4 group

implied “1” subscripton nitrogen, total 2 N

implied “1” subscripton sulfur, total 1 S

stated “3” subscripton oxygen, total 6 O

stated “4” subscripton oxygen, total 4 O

Example – Naming Ionic Substances when there is a Polyatomic Ion: Na2SO4

• Identify Major Class: Na is a metal because it is on the left side of the PT SO4

2- is a polyatomic ion: Ionic

2. Identify the Subclass: compound has 3 elements: Ionic with a Polyatomic Ion

3. Is the metal Type I or Type II? Na is in Group IA: Type I

• Identify the ions: Na = Na+ because it is in Group 1SO4

2- = SO42- is a polyatomic ion

5. Name the cation: Na+ = sodium ion (Type I)

6. Name the anion: SO42- = sulfate ion

7. Write the name of the cation followed by the name of the anionsodium sulfate

Example – Naming Ionic substances with Polyatomic Ion: Fe(NO3)3

1. Identify Major Class: Fe = is a metal because it is on the left side of the Periodic Table

NO31- = is a polyatomic ion: Ionic

2. Identify the Subclass: there are 3 elements: Ionic with a Polyatomic Ion

3. Is the metal Type I or Type II? Fe is not in Group IA, IIA, or (Al, Ga, In): Type II

4. Identify the ions: NO3 = NO3- is a polyatomic ion

Fe = Fe+3 to balance the charge of the 3 NO3-1

5. Name the cation: Fe+3 = iron(III) ion (Type II)

6. Name the anion: NO3- = nitrate ion

7. Write the name of the cation followed by the name of the anioniron(III) nitrate

Additional Examples

Name the following compounds:

PbCO3

Ca(HCO3)2

Fe(OH)2

Cu(NO3)2

NH4I

KHSO4

Additional Examples

Name the following compounds:

PbCO3 lead(II) carbonate

Ca(HCO3)2 calcium hydrogen carbonate

Fe(OH)2 iron(II) hydroxide

Cu(NO3)2 copper(II) nitrate

NH4I ammonium iodide

KHSO4 potassium hydrogen sulfate

Naming Acids

• Contain H3O+1 cation and an anion in an aqueous solution

• Binary acids have H3O+1 cation and a nonmetal anion

• Oxyacids have H3O+1 cation and a polyatomic anion

• Acids are molecular compounds that often behave like they are made of ions

• All names have acid at the end• Binary Acids = hydro prefix + stem of the name of

the nonmetal + ic suffix See Table 5.5• Oxyacids See Table 5.6

– if the polyatomic ion ends in –ate = name the polyatomic ion with an –ic suffix

– if the polyatomic ion ends in –ite = name the polyatomic ion with an –ous suffix

Example – Naming Binary Acids

HCl

1. Identify Major Class: first element listed is H, Acid

2. Identify the Subclass: 2 elements, Binary Acid

3. Identify the anion: Cl = Cl-, chloride because it is in Group 7A

4. Name the anion with an –ic suffix: Cl- = chloride chloric

4. Add a hydro- prefix to the anion name: hydrochloric

4. Add the word acid to the end: hydrochloric acid

Example – Naming OxyacidsH2SO4


2. Identify the Subclass: 3 elements in the formula, Oxyacid

3. Identify the anion: SO4 = SO42- = sulfate

• If the anion has –ate suffix, change it to –ic. If the anion has –ite suffix, change it to –ous: SO4

2- = sulfate sulfuric

4. Write the name of the anion followed by the word acid

sulfuric acid

Example – Naming Oxyacids H2SO3


2. Identify the Subclass: 3 elements in the formula, Oxyacid

3. Identify the anion: SO3 = SO32- = sulfite

4. If the anion has –ate suffix, change it to –ic. If the anion has –ite suffix, change it to –ous: SO3

2- = sulfite sulfurous

4. Write the name of the anion followed by the word acid

sulfurous acid

Additional Examples

Name the following acids:

• HF

• H3PO3

• HNO3

• HBrO4

• H2S

Additional Examples

Name the following acids:

• HF hydrofluoric acid

• H3PO3 phosphorous acid

• HNO3 nitric acid

• HBrO4 perbromic acid

• H2S hydrosulfuric acid

Formula-to-Name Flow Chart

Formula-to-NameStep 1

Is the compound one of the exceptions to the rules?

Common Names - Exceptions

• H2O = water, steam, ice

• NH3 = ammonia

• CH4 = methane

• NaCl = table salt

• C12H22O11 = table sugar


What major class of compound is it?

Ionic or Molecular

Major Classes

• Ionic

– metal + nonmetal

• The metal is written first in the formula

• Binary Ionic

– compounds with polyatomic ions

• Molecular

– 2 nonmetals

• Binary Molecular (or Binary Covalent)

– Acids – formula starts with H

• although acids are molecular, they behave as ionic substances when dissolved in water

• They may be binary or an oxyacid


What major subclass of compound is it?

Binary Ionic, Ionic with Polyatomic Ions,

Binary Molecular,

Binary Acid, Oxyacid

Classifying Compounds into major subclasses

• Compounds containing a metal and a nonmetal = binary ionic– Type I and II

• Compounds containing two nonmetals = binary molecular compounds –Type III

• Compounds containing a polyatomic ion = ionic with polyatomic ion

• Compounds containing H and a nonmetal = binary acids

• Compounds containing H and a polyatomic ion = oxyacids


Apply Rules for the Class and Subclass

Formula-to-NameRules for Ionic

• Made of cations and anions

• Name by simply naming the ions

– If the cation is:

• Type I metal = metal name

• Type II metal = metal name with the charge written in parentheses as a Roman Numeral

• Polyatomic ion = name of polyatomic ion

– If the anion is:

• Nonmetal = stem of nonmetal name + ide

• Polyatomic ion = name of polyatomic ion

Monatomic Nonmetal Anion

• determine the charge from the position on the Periodic Table

• to name the anion, change the ending on the element name to –ide

4A = -4 5A = -3 6A = -2 7A = -1

C = carbide N = nitride O = oxide F = fluoride

Si = silicide P = phosphide S = sulfide Cl = chloride

Periodic Pattern of Polyatomic Ions-ate groups

BO3-3 NO3

-1

SiO3-2 PO4

-3 SO4-2 ClO3

-1

AsO4-3 SeO4

-2 BrO3-1

TeO4-2 IO3

-1

CO3-2

IIIA IVA VA VIA VIIA

Patterns for Polyatomic Ions

• -ate ion

– chlorate = ClO3-1

• -ate ion + 1 O same charge, per- prefix

– perchlorate = ClO4-1

– \

• -ate ion – 1 O same charge, -ite suffix

– chlorite = ClO2-1

• -ate ion – 2 O same charge, hypo- prefix, -ite suffix

– hypochlorite = ClO-1

Practice - What are the formulas for compounds made from the following ions?

• copper(II) ion with a nitride ion

• iron(III) ion with a bromide ion

• aluminum ion with a sulfate ion

• Cu2+ with N3- Cu3N2

• Fe+3 with Br- FeBr3

• Al+3 with SO42- Al2(SO4)3

Formulas Describe Compounds

• A compound is a distinct substance that is composed of atoms of two or more elements.

• Formulas describe a compound by showing the number and type of each atom in the simplest unit of the compound:– molecules or ions: H2O, NaCl

• Each element in a compound formula is represented by the chemical symbol that identifies the element: NaCl, sodium chloride

• The number of atoms of each element is written to the right of the element as a subscript:– if there is only one atom, the 1 subscript is not written and is understood:

CO, carbon monoxide; CO2, carbon dioxide

• polyatomic groups are placed in parentheses: – if more than one group is part of the formula the number of groups is

written as a subscript:

Formulas Describe Compounds

Water = H2O –

two atoms of hydrogen and 1 atom of oxygen

Table sugar = C12H22O11 –

12 atoms of C, 22 atoms of H and 11 atoms of O

Writing the Formulas from the Names

• For binary molecular compounds, use the prefixes to determine the subscripts

• For Type I, Type II, Ternary Compounds and Acids

1. Determine the ions present

2. Determine the charges on the cation and anion

3. Balance the charges to get the subscripts

Example – Binary Moleculardinitrogen pentoxide

• Identify the symbols of the elements

nitrogen = N

oxide = oxygen = O

• Write the formula using the prefix “number” for the subscript

di = 2, penta = 5

N2O5

Example – Ionic Compoundsmanganese(IV) sulfide

1. Write the symbol for the cation and its charge

2. Write the symbol for the anion and its charge

3. Charge (without sign) becomes subscript for other ion

4. Reduce subscripts to smallest whole number ratio

5. Check that the total charge of the cations cancels the total charge of the

anions

Mn+4

S2-

Mn+4 S2- Mn2S4

Mn = (1)∙(+4) = +4S = (2)∙(-2) = -4

MnS2

Example – Ionic CompoundsIron(III) phosphate





5. Check that the total charge of the cations cancels the total charge of the anions

Fe+3

PO43-

Fe+3 PO43- Fe3(PO4)3

Fe = (1)∙(+3) = +3PO4 = (1)∙(-3) = -3

FePO4

Example – Ionic Compoundsammonium carbonate





5. Check that the total charge of the cations cancels the total charge of the

anions

NH4+

CO32-

NH4+ CO3

2- (NH4)2CO3

NH4 = (2)∙(+1) = +2CO3 = (1)∙(-2) = -2

(NH4)2CO3

Example – Binary Acidshydrosulfuric acid






H+

S2-

H+ S2- H2S

H = (2)∙(+1) = +2S = (1)∙(-2) = -2

H2S

in all acids the cation is H+

hydro meansbinary

Example – Oxyacidscarbonic acid






H+

CO32-

H+ CO32- H2CO3

H = (2)∙(+1) = +2CO3 = (1)∙(-2) = -2

H2CO3

in all acids the cation is H+

no hydro meanspolyatomic ion

-ic means -ate ion

Practice - What are the formulas for the following acids?

• chlorous acid

• phosphoric acid

• hydrobromic acid

• H+ with ClO2– HClO2

• H+ with PO43– H3PO4

• H+ with Br– HBr

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Classifying Materials