Ionic CompoundsIonic Compounds

Chemistry Joke

Q: Why do chemists like nitrates so much?

A: They’re cheaper than day rates!

A Review IonIon: atom or group of atoms that have a positive or : atom or group of atoms that have a positive or

negative chargenegative charge

Ions form when an atom or group of atoms gains or Ions form when an atom or group of atoms gains or loses loses electronselectrons

METALS METALS loselose electrons to form positive CATIONS. electrons to form positive CATIONS.

NONMETALS NONMETALS gaingain electrons to form negative electrons to form negative ANIONSANIONS

Monatomic IonsMonatomic Ions Ions consisting of only 1 atomIons consisting of only 1 atom

– The charge for ions formed from representative The charge for ions formed from representative elements can be determined by looking at the elements can be determined by looking at the periodic tableperiodic table

Group 1A metals form cations with a 1+ chargeGroup 1A metals form cations with a 1+ charge Group 2A metals form cations with a 2+ chargeGroup 2A metals form cations with a 2+ charge Group 3A metals form cations with a 3+ chargeGroup 3A metals form cations with a 3+ charge Group 5A nonmetals form anions with a 3- chargeGroup 5A nonmetals form anions with a 3- charge Group 6A nonmetals form anions with a 2- chargeGroup 6A nonmetals form anions with a 2- charge Group 7A nonmetals form anions with a 1- chargeGroup 7A nonmetals form anions with a 1- charge Group 8A elements do not form ionsGroup 8A elements do not form ions

Having One Having One Atom!Atom!

Polyatomic IonsPolyatomic Ions Tightly bound groups of atoms that behave as Tightly bound groups of atoms that behave as

a unit and carry a chargea unit and carry a charge Ex: The 10 you had to memorize.Ex: The 10 you had to memorize. 1- charge: 1- charge: 2- charge:2- charge: 3- charge:3- charge: 1+ charge: 1+ charge:

NO3- NO2

- OH- ClO3- C2H3O2

-

CO32- SO4

2- SO32-

PO43-

NH4+

Having Many Having Many Atoms!Atoms!

Naming Monatomic CationsNaming Monatomic Cations

The The name of a cation is the SAME as the name of the element!!

Ex: Na atom forms a sodium cationEx: Na atom forms a sodium cation Ex: Li atom forms a lithium cationEx: Li atom forms a lithium cation

How would you name the following ion:How would you name the following ion: AlAl+3+3 Aluminum ion

Naming Monatomic AnionsNaming Monatomic Anions

The name of a The name of a MONAtomicMONAtomic ion ends in ion ends in “ide”“ide”

Ex: Chlorine atom gains 1 electron to become Ex: Chlorine atom gains 1 electron to become the the CHLORIDECHLORIDE anion anion

Ex: Oxygen gains 2 electrons to become an Ex: Oxygen gains 2 electrons to become an anion named anion named OXIDEOXIDE

What would we name the following ion?What would we name the following ion?SS-2-2 Sulfide ion

Practice:Practice:

What do we call:What do we call:– A strontium atom when it loses 2 electronsA strontium atom when it loses 2 electrons

– An iodine atom when it gains 1 electronAn iodine atom when it gains 1 electron

– A phosphorus atom when it gains 3 A phosphorus atom when it gains 3 electrons? electrons?

Strontium ion

Iodide ion

Phosphide ion

Naming Ionic Naming Ionic CompoundsCompounds The cation comes 1The cation comes 1stst and keeps its name. and keeps its name. Monatomic anions end in “ide”Monatomic anions end in “ide” Polyatomic cations and anions keep their Polyatomic cations and anions keep their

names.names.Lithium ChlorideLithium Chloride

Magnesium FluorideMagnesium Fluoride

LiClLiCl

MgFMgF22

NHNH44ClCl

Be(OH)Be(OH)22

LiNOLiNO33 MgCOMgCO33

KK22SOSO44

Ammonium ChlorideAmmonium Chloride

Beryllium HydroxideBeryllium Hydroxide

Lithium NitrateLithium Nitrate

Magnesium CarbonateMagnesium Carbonate

Potassium SulfatePotassium Sulfate

Writing the Formulas!Writing the Formulas!

Cations and anions combine in a whole number Cations and anions combine in a whole number ratio that produces a ratio that produces a neutralneutral compound.compound.

The total positive charge of the cations will The total positive charge of the cations will equal the total negative charge of the anions.equal the total negative charge of the anions.

For example: For example: 11 Al Al+3+3 combines with combines with 33 F F-1-1

(1 x (1 x ++3) cancels with (3 x 3) cancels with (3 x --1)1)

1.1. Write the ions with their chargesWrite the ions with their chargesThe charges are known from the periodic The charges are known from the periodic table or memorized for polyatomic ions.table or memorized for polyatomic ions.

2.2. Cross the charge numbersCross the charge numbers (dropping the (dropping the + or -) to form the subscripts. (+ or -) to form the subscripts. (Subscripts Subscripts of 1 are not written.)of 1 are not written.)

3.3. Simplify the subscriptsSimplify the subscripts to the lowest to the lowest whole number ratiowhole number ratio

3 Step Process for Writing Ionic Formulas

Criss Cross Method

Writing Formulas for Ionic CompoundsWriting Formulas for Ionic Compounds Write the formula for magnesium chloride.Write the formula for magnesium chloride.

1.1. Write the ions with their chargesWrite the ions with their chargesThe charges are known from the periodic table.The charges are known from the periodic table.

2.2. Cross the charge numbersCross the charge numbers (dropping the + (dropping the + or -) to form the subscripts. (or -) to form the subscripts. (Subscripts of 1 Subscripts of 1 are not written.)are not written.)

3.3. Simplify the subscriptsSimplify the subscripts to the lowest whole to the lowest whole number rationumber ratio

Magnesium is in Magnesium is in Group 2A and Group 2A and forms a 2+ charge.forms a 2+ charge.

Chlorine is in Chlorine is in Group 7A and Group 7A and forms a 1- charge.forms a 1- charge.

MgMg2+2+ ClCl1-1-

MgMg ClCl

MgClMgCl22

Writing Formulas for Ionic CompoundsWriting Formulas for Ionic Compounds Write the formula for beryllium oxide.Write the formula for beryllium oxide.

1.1. Write the ions with their chargesWrite the ions with their chargesThe charges are known from the periodic table.The charges are known from the periodic table.

2.2. Cross the charge numbersCross the charge numbers (dropping the + (dropping the + or -) to form the subscriptsor -) to form the subscripts

3.3. Simplify the subscriptsSimplify the subscripts to the lowest whole to the lowest whole number ratio. (If both subscripts are the number ratio. (If both subscripts are the same, they can be dropped.)same, they can be dropped.)

Beryllium is in Beryllium is in Group 2A and Group 2A and forms a 2+ charge.forms a 2+ charge.

Oxygen is in Group Oxygen is in Group 6A and forms a 2- 6A and forms a 2- charge.charge.

BeBe2+2+ OO2-2-

BeBe OO

BeBe22OO22

BeOBeO

Writing Formulas for Ionic CompoundsWriting Formulas for Ionic Compounds

Follow the same 3 steps.Follow the same 3 steps. Just add parentheses around the Just add parentheses around the

polyatomic ion before it gets a subscriptpolyatomic ion before it gets a subscript

With Polyatomic IonsWith Polyatomic Ions

Write the formula for calcium hydroxide.Write the formula for calcium hydroxide.1.1. Write the ions with their chargesWrite the ions with their charges

2.2. Cross the charge numbersCross the charge numbers (dropping the + or -) to form the subscripts(dropping the + or -) to form the subscripts3.3. Subscripts of 1 are not written Subscripts of 1 are not written 4.4. Simplify the subscripts Simplify the subscripts

5.5. Remember to add parentheses around the Remember to add parentheses around the polyatomic ion if a subscript has been polyatomic ion if a subscript has been added!added!

Writing Formulas for Polyatomic Ionic CompoundsWriting Formulas for Polyatomic Ionic Compounds

Calcium is in Group Calcium is in Group 2A and forms a 2+ 2A and forms a 2+ charge.charge.

Hydroxide is a Hydroxide is a polyatomic ion that polyatomic ion that has a 1- charge.has a 1- charge.

CaCa2+2+ OHOH1-1-

CaCa OHOH

CaOHCaOH22There are 2 Hydroxide ions There are 2 Hydroxide ions not just 2 Hydrogen atoms.not just 2 Hydrogen atoms. Ca(OH)Ca(OH)22

Try SomeTry Some Sodium CarbonateSodium Carbonate Potassium HydroxidePotassium Hydroxide Magnesium PhosphateMagnesium Phosphate

NaNa22COCO33

KOHKOHMgMg33(PO(PO44))22

Chemistry Joke

Q: What happened when someone told a joke to two helium atoms?

A: They went, “He He!!”