Ionic Bonding Day 2

EQ: What are the guidelines to write and name Ionic formulas?

Writing Ionic Formulas

• Binary compounds are made up of two elements.

• Binary ionic compound are made up of a metal and a nonmetal.

Writing ionic formulasEx: potassium chloride1. Write symbols for both

ions including charges2. Check to see if charges

balance

K+ Cl-

Balanced!

Formula is: KCl

Writing ionic formulasEx: calcium bromide1. Write symbols for both

ions2. Check to see if charges

balance3. If not balanced use

subscripts to balance charges

Ca2+

Formula is: CaBr2

Br-

Not balanced!

1(2+) + 2(1-) = 0

Writing Ionic FormulasEx: calcium sulfide1. Write Symbols2. Crisscross3. Check to see if

subscripts can be reduced

Ca2+ S2-

Formula is: Ca2S2

Reduce!!

Formula is: CaS

Correct!!

Predicting Ionic Charges• Groups 3-12:Many transition elements have more than

one chargeIron(II) = Fe2+ Iron(III) = Fe3+

If an element forms more than one ion, a Roman numeral is used to indicate the charge

Predicting Ionic Charges• Groups 3-12:Some transition elements have only one

oxidation state

Zinc = Zn2+ Silver = Ag+

No Roman numeral is used for elements that have only one oxidation state

Writing Ionic FormulasEx: Iron(III) Oxide1. Write all symbols2. Check to see if charges

balance3. Use subscripts to

balance

Fe3+ O2-

Not balanced!

Formula is: Fe2O3

2(3+) + 3(2-) = 0

Writing Ionic FormulasEx: Iron(III) oxide• Another method for

writing balanced formulas is the crisscross method

• First write symbols• Charge of one ion is used

as subscript for other ion

Fe3+ O2-

Fe2O3

Writing ionic formulasRemember the Steps

• Write symbols• Crisscross• Reduce if needed

You Practice

Sodium iodideTin(IV) chloridePotassium sulfideCalcium iodide

Polyatomic ions

• Polyatomic ions are tightly bound groups of atoms that behave as a unit and carry a charge.

• For instance the sulfate anion, SO42-,is

made up of one sulfur atom and four oxygen atoms and has a 2- charge.

• You will need a list of polyatomic ions to determine the name and formula

Writing ionic formulas

• Ionic compounds that contain a polyatomic ion are called ternary ionic compounds

• The names usually end in ate or ite and you need to remember to look up the formula of the polyatomic ion

Writing ionic formulasEx: calcium nitrate• Write symbols• Crisscross to balance• If the polyatomic ion

requires a subscript, place parentheses around the ion

Ca2+ NO3-

Ca (NO3)

2

Writing ionic formulasEx: lithium carbonate• Write symbols• Crisscross and write

formula using parentheses if needed

• Notice that no parentheses are needed if only one polyatomic ion

Li+ CO32-

Li2CO3

Writing ionic formulasEx: magnesium hydroxide

• Remember that the hydroxide ion also needs parentheses

Mg2+ OH-

Mg(OH)2

Writing Ionic FormulasRemember the Steps

• Write symbols• Crisscross• Use parentheses if

needed• Reduce subscripts if

needed

You Practice!

ammonium sulfitecalcium phosphatemagnesium carbonate

Naming Ionic CompoundsEx: NaI

• Name the first ion• Name the second ion• Remember that negative

ions end in ide

The name of the compound is:

sodium iodide

Naming Ionic CompoundsEx: CuO• Name the first ion• Recall that the copper ion

can be either Cu+ or Cu2+ • Since O has a 2- charge

is must be Cu2+ or Copper(II)

• Name the second ion

The name of the compound is:

copper(II) oxide

Naming Ionic CompoundsRemember the Steps• Name the first ion• Check to see if it needs a

roman numeral• Name the second ion

You Practice!!

ZnSKCl

CuBr2

FeS

Naming Ionic CompoundsEx: K2Cr2O7

• If a formula contains three or more elements, it contains a polyatomic ion

• You must look up the name

• Cr2O72- is the

permanganate ion

The name of the compound is:

potassium permanganate

Naming Ionic CompoundsRemember the Steps• Name the first and

second ions• Remember to check if the

metal requires a roman numeral

• If it is a ternary compound look up the polyatomic ion

You practice!!

CaC2O4

Li2S04

Sn3(PO4)2