Chapter 8 Notes, part I Writing Ionic Formulas. Compounds Up until now, we have only looked at...

Chapter 8 Notes, Chapter 8 Notes, part Ipart I

Writing Ionic Writing Ionic FormulasFormulas

CompoundsCompounds

•Up until now, we have only looked at single elements.

•There are only (to date) just over 100 elements, so how do we account for there being so many different types of stuff?

CompoundsCompounds•There are millions of different compounds—two or more elements that are combined chemically.

•The two types of compounds we will discuss in this chapter are ionic compounds and covalent compounds.

A A compoundcompound is a pure is a pure substance made up of two substance made up of two or more elements thator more elements that are chemically joined in definite proportions.

Ex. Carbon dioxide is CO2 , while carbon monoxide (the poison) is CO .

2 oxygen atoms

1 oxygen atom

Compounds do not look or act like the elements that form them.

•Sodium is a silvery metal that reacts violently with water

•Chlorine is a

poisonous, green

gas.

•Does salt share any of those properties?

Oxygen + Hydrogen -----> Water

Hydrogen is explosive!

Is water explosive?

Ionic Ionic CompoCompouundsnds•Last chapter we discussed ions—elements that have a charge due to losing or gaining electrons.

•Ionic compounds are made of ions.

Ionic Ionic CompoCompouundsnds• Metals tend to form ions by losing

electrons, giving them an overall positive charge. These are called cations.

• Nonmetals tend to form ions by gaining electrons, giving them an overall negative charge. These are called anions.

Ionic Ionic CompoCompouundsnds•An ionic compounds is

formed from a cation and an anion, which means they are usually formed from a metal and a nonmetal.

IONIC Compounds

Ionic compounds consist of two oppositely charged ions. Li+1 F-1

Positive ion – metal Negative ion - nonmetal

9p+

10n03p+

4n0Li0 F0F-1Li+1

Covalent compounds occurCovalent compounds occurbetween two nonmetals.between two nonmetals.

Both nonmetals share electronsBoth nonmetals share electrons

8p+

8n0

6p+

6n0

8p+

8n0

Carbon dioxideCarbon dioxide

Atoms are stable, or resistant to change if their outer energy level is completely filled with electrons.

10p10n

NEON

Atoms of all the Atoms of all the elements have elements have from one to sevenfrom one to sevenelectrons inelectrons intheir outer energytheir outer energylevel level except the noble except the noble gasesgases..

3p4n

9p10n

When atoms lose or gainWhen atoms lose or gain Electrons they becomeElectrons they become

ions.ions.

Na+1

Cl -1Al +3

P-3

Mg+2

O-2

Single or Monoatomic ions

Ionic Ionic CompoCompouundsnds•Anions and cations can also

be made up of a group of elements bonded together that carry an overall charge.

•These groups of elements are called polyatomic ions.

PPolyatomic ionsolyatomic ions - - groups of groups of 2 or more elements that have 2 or more elements that have aa chargecharge

PO4-3

SO4-2

NH4+1

CO3-2NO4

-1

NO3-1

SO3-2

ClO3-1

C2H3O2-1

Ionic Ionic CompoCompouundsnds•Even though an ionic

compound is made from charged particles, it is still electrically neutral.

•This means that its total charge is always EQUAL TO ZERO!!!

Ionic Ionic CompoCompouundsnds•SIDENOTE: The smallest

part of an ionic compound is called a formula unit—just like the smallest part of an element is called an atom.

Chemical Chemical FoForrmulasmulas•A chemical formula is like

the recipe of a compound—it tells you the type and number of each element in the compound.

Compounds are written as Compounds are written as formulas.formulas.

Formula - a group of symbols, possibly with subscripts, showing the number and type of atoms forming the compound.

Na2SO4 Ba3(PO4)2

Formulas consist of a Formulas consist of a positivepositive ion and a ion and a negativenegative ion. ion.

Na+1

Cl -1Al +3

P-3

Mg+2

O-2

NaCl MgO AlP

The positive ion always comes 1st

The The positivepositive ion is ion is written written firstfirst!!!!!!!!!!!!!!!!

We read from left to right….Metals are on the left.(LEFT = LOSE e- = positively charged ions)

Metals are first !!!!!

Na+1 Cl-1

Nonmetals are on the Nonmetals are on the rightright……and and GAIN e-GAIN e- = = negative ionsnegative ions Nonmetals are second!!!!!Nonmetals are second!!!!!

NaCl

Na+1 Cl-1

Subscript - a small lowered number that shows number ofatoms of each element in the compound.

Ba3P2

Ba BaBa P P

A subscript of (1) A subscript of (1) is NEVER written.is NEVER written.

NaNa11ClCl11 NO!!!

Oxidation number - the charge of an atom, indicating whether the atom has lost (+) or gained (-) electrons and how many electrons it lost or gained.

AlAlSuperscript

+3

OxidatioOxidationn Numbers Numbers

Group Lose or gainelectrons

How many OxidationNumber

1A lose 1 +1




1A lose 1 +1

2A lose 2 +2




1A lose 1 +1

2A lose 2 +2

3A lose 3 +3




1A lose 1 +1

2A lose 2 +2

3A lose 3 +3

4A Lose or gain 4 +4 or -4




1A lose 1 +1

2A lose 2 +2

3A lose 3 +3


5A gain 5 -3




1A lose 1 +1

2A lose 2 +2

3A lose 3 +3


5A gain 3 -3

6A gain 2 -2




1A lose 1 +1

2A lose 2 +2

3A lose 3 +3


5A gain 3 -3

6A gain 2 -2

7A gain 1 -1




1A lose 1 +1

2A lose 2 +2

3A lose 3 +3


5A gain 3 -3

6A gain 2 -2

7A gain 1 -1

8A none none 0

The The total charge on a total charge on a compound must add up to compound must add up to ZERO.ZERO.

Ca CaO

OO-2Ca+

2 +2 -2 = 0

IONIC COMPOUNDS

Ionic compounds consist of aIonic compounds consist of a

Positive metal oror positive polyatomic ionion

Negative nonmetal oror negative polyatomic

ionion

Binary compounds are composed of only two elements.(Look for 2 capital letters!)

Ex. NaCl sodium chlorideEx. Mg3N2 magnesium nitride

Polyatomic compoundsPolyatomic compounds are are composed of composed of three or morethree or more elementselements and contain at and contain at least one polyatomic ion.least one polyatomic ion.(Look for 3 or more capital(Look for 3 or more capitalletters)letters)

NaC2H3O2

1 2 3 4

Polyatomic ions

Ex. Ex. Na Na ClOClO33 sodium chlorate sodium chlorate

Ex. Ex. CaCa33 ( (POPO44))2 2 calcium phosphate calcium phosphate

Variable and Non-variableVariable and Non-variableMetals

(positive ions)

A practical approach to determining if a metal is variable

or non-variable.

VARIABLE

If the metal is on the back of the periodic table with more than one oxidation number listed it is variable.

EX: Cr= +2, +3, or +6EX: Cr= +2, +3, or +6 Fe= +2, or +3Fe= +2, or +3

Look at the chart on the back of periodic table.

Look at the Look at the chartchart on the back of on the back of periodic table.periodic table. NON VARIABLE

If it is not on the back of the periodic table

OROnly one choice of oxidation numberlisted. EX: Ag+1, Zn+2, or Ni+2

Then it is non variable

ROMAN NUMERALS

Used when a metal has morethan one potential oxidationnumber.

The name of the metalmust tell you the valence ofthe metal

Chromium chlorideChromium chlorideIII

III The Roman numeralthree tells you thatthe oxidation numberof the metal is +3.

Chromium chlorideVI

VI The Roman numeralsix tells you thatthe oxidation numberof the metal is +6.

Writing and Writing and Naming Ionic Naming Ionic CompoundsCompounds

Writing ChemicWriting Chemicaal l FormulasFormulas

1) Write the symbol for the elements and their oxidation number, positive ion first (the metal).EX: For a compound of Magnesium and ChlorineEX: For a compound of Magnesium and Chlorine

Mg+2 Cl-1

Writing ChemicWriting Chemicaal l FormulasFormulas2) Criss cross the numbers and

write them as subscripts without the signs.

Mg Cl+2 -12 1

Writing ChemicWriting Chemicaal l FormulasFormulas3) If there is a one charge, do

not write it.

Mg1Cl2Mg Cl2

Writing ChemicWriting Chemicaal l FormulasFormulas4) If you have subscripts that

are multiples, reduce them down.

Pb O+4 -24 2

21

Naming Ionic Naming Ionic CCompoundsompounds

For ionic compounds where the metal always has the same oxidation number,

1) Name the metal.EX: BaBrEX: BaBr22

Barium


For ionic compounds where the metal always has the same oxidation number,

2) Write the name of the non-metal, and change the end to –ide. Barium brom ine ide

EX: BaBrEX: BaBr22

Naming Binary Non Naming Binary Non variablevariableCompoundsCompounds

1. Name the positive ion2. Name the negative ion changing the ending to

IDE.

AlBrAlBr33

Aluminum bromideAluminum bromide

No Roman numeral is needed

-ides-idesN - Nitrogen--> NitrideO – Oxygen --> Oxide

F - Fluorine--> Fluoride

P - Phosphorus--> Phosphide

S - Sulfur--> Sulfide

Cl - Chlorine-->ChlorideCl - Chlorine-->Chloride

Br - Bromine -->Bromide

I - Iodine--> Iodide

Naming Polyatomic Non variableCompounds

1. Name the positive ion 2. Name the negative ionchanging the ending to -ate.changing the ending to -ate. AlPOAlPO44 AluminumAluminum

No Roman numeral is needed

PhosphatPhosphatee


If there is a polyatomic anion, then you do not change the ending: EX: Ca(NOEX: Ca(NO33))22

Calcium nitrate

Name These:

Na2O

MgCl2Na2CO3

Naming binary compoundsNaming binary compoundsof variable metalsof variable metals

Determine the oxidation number of the variable metal using the crisscross method

Cr2O3

Cr+ O-

The oxidation number of the The oxidation number of the chromium is chromium is +3+3 The name is The name is ChromiumChromium IIIIII oxideoxide

3322

Naming Ionic Naming Ionic CCompoundsompounds3)3)If a positive ion (a metal) can If a positive ion (a metal) can

have more than one oxidation have more than one oxidation number, you have to designate number, you have to designate its charge in the name!its charge in the name!

We do this by putting the charge We do this by putting the charge as a roman numeral in as a roman numeral in parenthesis between the parenthesis between the positive positive and negative and negative

ion.ion.

Naming Ionic Naming Ionic CCompoundsompoundsWhy do we need to do that?

Name: Fe2O3

FeO

These both exist in nature, so we have to show which one we mean.


Fe2O3Name it:

Iron ox ygen ide ( ) III

-2

If this is true, then what was iron to begin with?

+3 Reverse criss cross to find the charge of

the iron:

Reverse criss cross to find the charge of

the iron:


Fe OName it:

Iron ox ygen ide ( ) II

-1

If this is not true, the numbers must have been reduced.

+2 -2

Naming Ionic Naming Ionic CCompoundsompoundsMetals that don’t need parentheses:Group I, II and IIIAZn, Cd (always +2) and Ag (always

+1)

Which means transition, inner transition and other metals do!

Naming polyatomic compoundsof variable metals

Determine the valence of the variable metal using the crisscross method

Hg2SO4

Hg++ SO4--

The oxidation number of the The oxidation number of the Mercury is +1Mercury is +1

Mercury I sulfate

1122

Naming Ionic Naming Ionic CCompoundsompoundsFinal flowchart of how to name:

Name the positive ion.

Does it need a roman numeral?

If so, reverse criss cross, if not, ignore.

Name the negative ion and:

If a nonmetal end in -ide; if not, end normally

Name these:

Na2S

CuCl2K2SO4

Pb(NO3)3

Finding formulas1.Determine the charge of each side of the formula. Nonvariables:Aluminum oxide: Aluminum oxide: AlAl+3+3 O- O-22 Potassium Chloride KPotassium Chloride K+1+1 Cl Cl-1 -1

Calcium nitrate Ca Calcium nitrate Ca +2+2 NO NO33-1-1

2. Add the oxidation numbers together.

+3-2 = +1 +1-1 = 0 +2-1 = +3-2 = +1 +1-1 = 0 +2-1 = +1+1

2. Add the oxidation numbers together. AlAl+3+3 O O-2-2 K K+1+1 Cl Cl-1-1

+3-2 = +1 +1-1 = +3-2 = +1 +1-1 = 00

3. If the total = zero the formula is balanced with one

ion each ex: KClex: KCl

If the total does not equal zeroIf the total does not equal zerouse the crisscross method touse the crisscross method todetermine the number of ionsdetermine the number of ionsneeded for each side of the needed for each side of the formulaformula..

Al+3+3 O-2-2

Al O

33 22

If the total does not equal zeroIf the total does not equal zerouse the crisscross method touse the crisscross method todetermine the number of ionsdetermine the number of ionsneeded for each side of the needed for each side of the formula.formula.

Al+3+3 SO4 -2-2

Al SO4

33 22

( )

Writing ChemicWriting Chemicaal l FormulasFormulas5) If using polyatomic ions, put

parentheses if there are more than one.

Ca NO3

+2 -12 1( )

Writing ChemicWriting Chemicaal l FormulasFormulasHere’s an example of a

polyatomic that doesn’t have parentheses.

Na PO4

+1 -31 3

Practice These:

Barium and chlorineRubidium and nitrogen Lithium and phosphate Iron (III) and nitrateManganese (IV) and sulfur

BaCl2Rb3NLi3PO4

Fe(NO3)3

MnS2

Chapter 8 Notes: Part III

Bonding in Metals

Metallic Bonds•Metallic bonds consist of metal cations with a free-floating “sea of electrons”

•This explains many physical properties—why metals are good conductors, and why they are malleable and ductile

Malleablilty/Ductility

•Ductile – the ablity to be drawn into wires

•Malleable – the ablity to be hammered into shapes

Malleablilty/Ductility•Metals display these characteristics because when subjected to pressure, cations can easily slide past one another (unlike ionic solids, which have very strong attractive and repulsive forces)

Alloys

•Most metals you use everyday are a mixture of two or more elements, for example brass, bronze or steel. These are called alloys.

Alloys

•The importance of alloys are that often they have superior properties than the elements they are made of.

Oxyanions

An oxyanion is a polyatomic ion composed of an element, usually a nonmetal, bonded to one or more oxygen atoms.

Many oxyaions contain the same nonmetal and have the same charges but differ in the number of oxygen atoms.

These ions are easily named using the following conventions.

• The ion with more oxygen atoms is named using the root of the nonmetal plus the suffix-ate.

• The ion with fewer oxygen atoms is named using the root of the nonmetal plus the suffix-ite.

Halogens form four oxyanions

• The ion with the greatest number of oxygen atoms is named using the prefix per-, the root of the nonmetal, and the suffix –ate.

• The ion with one less oxygen atom is named with the root of the nonmetal and the suffix –ate.

• The ion two fewer oxygen atoms is named using the root of the nonmetal plus the suffix –ite.

• The ion with three fewer oxygen atoms is named using the prefix hypo-, the root of the nonmetal, and the suffix –ite.

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