Formulas for Ionic Compounds

• Ionic compounds are made up of a METAL and a NONMETAL and are generally referred to as SALTS.

Writing a Formula Problem: Write the formula for the ionic compound that

will form between sodium and chlorine. • Write the symbol for sodium first (because it’s the metal)

along with its combining capacity. Then write the symbol for chlorine with its combining capacity.

• Na+ Cl –

• How do you know which is the metal? • It has a positive cc, and it’s further left on the periodic

table

• The goal is to balance the positive and negative charges to make a neutral compound

• Na+ Cl - are the charges balanced? • YES! • So the formula is… • NaCl

• What is the ionic formula for a compound of barium and bromine?

• Ba+2 Br - We need another Br – to balance the charges!

• Br -

• Thus, the formula is… • BaBr2

• Write the formula for lithium with oxygen. • Write the formula for magnesium with

oxygen.

• Li+ O-2

Li+

= Li2O • Mg+2 O-2

= MgO

Learning Check

Write the correct formula for the compounds containing the following ions:

A. Na+, S2- 1) NaS 2) Na2S 3) NaS2 B. Al3+, Cl- 1) AlCl3 2) AlCl 3) Al3Cl C. Mg2+, N3-

1) MgN 2) Mg2N3 3) Mg3N2

Naming Binary Ionic Compounds

● Contain 2 different elements ● Name the metal first with its regular name, then

the nonmetal as –ide ending. Examples:

1) NaCl 1) sodium chloride 2) ZnI2 2) zinc iodide 3) Al2O3 3) aluminum oxide

Learning Check

Complete the names of the following binary compounds:

Na3N sodium ________________ KBr potassium ________________

Al2O3 aluminum ________________

MgS _________________________

Solution

Complete the names of the following binary compounds:

Na3N sodium nitride

KBr potassium bromide

Al2O3 aluminum oxide

MgS magnesium sulfide

Learning Check

A. The formula for the ionic compound of Na+ and O2- is 1) NaO 2) Na2O 3) NaO2 What is the name of the compound? B. The formula of a compound of aluminum and

chlorine is 1) Al3Cl 2) AlCl2 3) AlCl3

What is the name of the compound?

Solutions

A. The formula for the ionic compound of Na+ and O2- is 2) Na2O The name is sodium oxide

B. The formula of a compound of aluminum and chlorine is

3) AlCl3 The name is aluminum chloride

Transition Metals with More than One Combining Capacity

• If the metal has more than one combining capacity, the specific combining capacity being used must be given in the name as a ROMAN NUMERAL in brackets after the metal name.

• Copper can be Cu+1 or Cu+2 • Iron can be Fe+2 or Fe+3

• Lead can be Pb+2 or Pb+4

• There are others as well…see the Per. Table or p. 341 in Hebden (Cations).

Naming Transition Metal Salts

Use a roman numeral after the name of a transition metal that possesses multiple combining capacities

FeCl3 (Fe3+) iron (III) chloride CuCl (Cu+ ) copper (I) chloride SnF4 (Sn4+) tin (IV) fluoride PbCl2 (Pb2+) lead (II) chloride Fe2S3 (Fe3+) iron (III) sulfide

Learning Check Complete the names of the following binary

compounds with variable metal ions: FeBr2 iron (_____) bromide

Cu2O copper (_____) oxide

SnCl4 ___(_____ ) ______________

Fe2O3 ________________________

CuS ________________________

Solutions Complete the names of the following binary

compounds with variable metal ions: FeBr2 iron ( II ) bromide

Cu2O copper ( I ) oxide

SnCl4 tin (IV) chloride

Fe2O3 iron (III) oxide

CuS copper (II) sulfide

Learning Check Name the following compounds: A. CaO - hint: does Ca have only one cc, or multiple cc? Do you

need a roman numeral?? 1) calcium oxide 2) calcium(I) oxide 3) calcium (II) oxide

B. SnCl4 1) tin tetrachloride 2) tin(II) chloride 3) tin(IV) chloride

C. Fe2O3

1) iron oxide 2) iron (III) oxide 3) iron trioxide

Solutions

Name the following compounds: A. CaO 1) calcium oxide B. SnCl4 3) tin(IV) chloride

C. Fe2O3 2) iron (III) oxide

Polyatomic Ions

• There are groups of atoms that tend to stay together (very stable) and carry an overall charge

• These groups are called polyatomic ions • There is a list of polyatomic ions in the back of your

Hebden text or on the back of your periodic table • All polyatomic ions except ammonium NH4

+ have negative charges and act as nonmetals

• Notice that many have an –ate or –ite ending…this can alert you that you are dealing with a polyatomic ion

• The charge on the polyatomic ions are also their combining capacity.

• Write the formula for the compound made with sodium and carbonate:

• Na+ CO3-2

• Na+ We needed one more Na+ to balance charges

• the formula is… • Na2CO3

• If you end up with two or more polyatomic ions in your formula, you need brackets!!

• Find the formula for the compound that has calcium and hydroxide

• Ca2+ OH –

• OH –

• The formula is… • Ca(OH)2

Naming Compounds with Polyatomic Ions

• Name like you would any other ionic compound but DON’T change the ending of the polyatomic ion

• Ca(OH)2 is.. • calcium hydroxide • FeCO3 is… • iron (II) carbonate

• Complete the Ionic Formula Writing/Naming worksheet.

• Complete the Polyatomic Ions worksheet.

This won’t get you anywhere!