Chapter 9 Notes, Chapter 9 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.

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 compound is

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

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.

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!!!

Chemical Chemical FoForrmulasmulas• 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.

• A chemical formula is like the recipe of a compound—it tells you the type and number of each element in the compound.

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

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

Naming Ionic Naming Ionic CompoundsCompounds

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

Naming Ionic Naming Ionic CCompoundsompounds

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 Ionic Naming Ionic CCompoundsompounds

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 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 number, you have to designate its charge in the designate its charge in the name!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.

Naming Ionic Naming Ionic CCompoundsompounds

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:

Naming Ionic Naming Ionic CCompoundsompounds

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 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)4