GO 4 Apply simplified chemical nomenclature in describing

elements, compounds and chemical reactions

4-2 Read and interpret chemical formulas for Ionic

compounds

Guided Question

How do we uses the information from the periodic table to write a chemical name and chemical formula

for an Ionic Compound?

3.1 Naming Compounds When two or more elements bond together,

they form one compound

A compound may be described by its proper name or its common name

A compound may also be described by its chemical formula

H2O CO2 NaCl

Chemical formulas indicate which elements (symbols) are in the compound and in what ratios (subscripted numbers)

IUPAC

IUPAC stands for the “International Union of Pure and Applied Chemistry” (1920)• An international group that decides how to name

compounds and approves the names of new elements

• This single method of naming compounds was universally adopted by all chemists/scientists

• We will be learning this strict set of rules to name compounds

Until 1920, there was not a universal system of naming so there were many names for the same compound!

the compound is the compound is aqueousaqueous (dissolved (dissolved in water) in water) eg. Ceg. C1212HH2222001111(aq)(aq)aqaq

the compound is a the compound is a gasgas eg. Heg. H22OO(g)(g)gg

the compound is a the compound is a liquidliquid eg. Heg. H22OO(l)(l)ll

the compound is a the compound is a solidsolid eg. Heg. H22OO(s)(s)ss

DescriptionDescriptionSymbSymbolol

Physical states are shown with all chemical formulas!Physical states are shown with all chemical formulas!

•States are at the end, subscripted, in brackets.States are at the end, subscripted, in brackets.

Working with Compounds

Go to pg. 142 – Working with compounds As a class we will go through the table

3.2: Ionic Compounds Ionic compounds are

created with ionic bonds

Ionic bonds occur as a result of opposite charge attraction caused by one atom of a metal group giving away one or more of it’s electrons to a non-metal atom. • This results in two IONS

which are now attracted to each other.

Na Cl

e-

Na+ Cl-

e-

becomes:

So what are IONS?Atoms that have lost or gained electrons are now

IONS:

•Anions are negatively charged ions resulting from GAINING one or more electrons

ex. Cl- is a chloride ion

•Cations are positively charged ions resulting from LOSING one or more electrons

ex. Na+ is a sodium ion

Cations and anions are naturally attracted to one another (opposite charges attract) – this attraction is called an ionic bond!

What motivates an atom to become an ion?

The ultimate goal of each element is to have the same number of electrons as the NEAREST noble gas

An element can either gain an electron(s) or lose an electron(s) to reach this goal

Examples

Sodium - Draw a Bohr diagram of sodium What would it like to do to have a full outer

energy level (be like its nearest noble gas)?

Oxygen – Draw a Bohr diagram of oxygen What would it like to do to have a full outer

energy level (be like its nearest noble gas)?

11 p+12 n°

2e– 8e– 1e–

Na

8 p+8 n°

2e– 6e–

O

IONS

11 p+12 n°

2e– 8e–

Na+

8 p+8 n°

2e– 8e–

O2 -

Where can you find ion charges? Besides drawing the Bohr diagram

every time, you can look at the periodic table to find what ions you are working with?

B – shows what ions are possible for titanium

Does anyone know what A, C, D and E stand for?

Ionic Compounds - Writing the Formula Binary ionic compounds are made up of one metal ion

and one non-metal ion.

All ionic compounds have an overall (net) electrical charge of zero

ex. sodium chloride Na+ (sodium ion) and Cl- (chloride ion)

form NaCl(s) (sodium chloride)

The positive charge on the sodium ion “cancels” out the negative charge on the chloride ion so the net electrical charge is zero (1+ + 1- = 0)

NaCl(s) is called the chemical formula

Ex.2 Chemical Name: calcium chloride

calcium ion has a charge of 2+

chloride ion has a charge of 1-

calcium ion (Ca2+) and 2 chloride ions 2(Cl-)

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

Chemical Formula: CaCl2(s)

To get a net electrical charge of zero we will need two chloride ions because each chloride ion has only 1 negative charge and 1 calcium ion has a

charge of positive 2

Ex.3 Chemical Name: aluminum chloride

aluminum ion has a charge of 3+

chloride ion has a charge of 1-

aluminum ion (Al3+) and 3 chloride ions 3(Cl-)

(+3) + 3(-1) = 0

Chemical Formula: AlCl3(s)

To get a net electrical charge of zero we will need three chloride ions because each chloride ion has only 1 negative charge and 1 aluminum ion has a

charge of positive 3

Step-By-Step of what we just did...

Rules for Writing Chemical Formulas

for Ionic Compounds

1. Write the metal ion symbol first, then the non-metal ion

2. Figure out how many of each ion is required to balance the charges

3. Write the formula by indicating how many atoms of each element are in it by using a subscript those numbers.

If the subscript is a 1, DO NOT write it in.

Short-cut method: CrissCross

Na+ (sodium ion) and Cl- (chloride ion)

Na+ Cl- Na1Cl1 NaCl

Ca2+ (calcium ion) and O2- (oxide ion)

Ca2+ O2- Ca2O2 CaO

(reduce to simplest whole number ratio)

This method ‘This method ‘criss-crosses’ the ion chargescriss-crosses’ the ion charges to to the subscript positionthe subscript position

IF you use criss-cross, IF you use criss-cross, be carefulbe careful to to simplifysimplify the formula keeping whole numbers!the formula keeping whole numbers!

You Try it!

Write the proper Write the proper chemical formulachemical formula for the for the following ion combinationsfollowing ion combinations

CaCa33PP2(s)2(s)CaCa2+2+ + P + P3-3-HH22SS(s)(s)HH1+1+ + S + S2-2-

PbOPbO2(s)2(s)PbPb4+4+ + O + O2-2-AlNAlN(s)(s)AlAl3+3+ + N + N3-3-

FeFe22OO3(s)3(s)FeFe3+3+ + O + O2-2-MgBrMgBr2(s)2(s)MgMg2+2+ + Br + Br1-1-

CuCu33NN2(s)2(s)CuCu2+2+ + N + N3-3-KFKF(s)(s)KK1+1+ + F + F1-1-

CompoundCompoundIonsIonsCompoundCompoundIonsIons

Remember, all ionic compounds are solids at room conditions . . .

Naming Ionic CompoundsFrom the chemical formula, can find the name of a compound. To do this, you need to know how to name a cation (the metal ion) and an anion (the non-metal ion):

cation – simply the element name followed by “ion”- transition metalstransition metals have more than one charge have more than one charge

possible, use possible, use Roman numeralsRoman numerals after the metal after the metal name to indicate which ion is presentname to indicate which ion is present

anion – change the end of the element name to ‘-ide’ followed by “ion”

Name the compound by writing the name of the cation (metal) then the name of the anion (non-metal)

ex. CaF2(s)

Ca2+ and F1-

name of the cation = calcium

name of the anion = fluoride

Name of the compound: calcium

fluoride

ex. CuF2(s)

Cu2+ and F1-

Name of the cation = copper(II) Name of the anion = fluoride

Name of the compound: copper(II) fluorideWhy do we need to specify which copper it is?

Because there are two options Cu2+ or Cu1+

POLYATOMIC IONS

Polyatomic ions are a group of atoms that together carry a negative charge (anion) or a positive charge (cation)

• The entire group of atoms behaves as one ion

• The entire group will carry the net charge (not just one of the atoms)

• Most polyatomic ions are negative (anions). The most common polyatomic cation is NH4

+ ,

the ammonium ion.

ex. chemical formula: CaCrO4(s)

calcium ion (Ca2+) and chromate ion (CrO42-)

name of the cation: calcium

name of the anion: chromate

Don’t change the names of ions from the polyatomic ion table – leave them alone!

Name of the compound: calcium chromate

Naming the compound from the chemical formula:

Determining the chemical formula from the name:

ex. Compound Name: magnesium nitrate

magnesium ion has a charge of 2+

nitrate ion has a charge of 1-

magnesium ion (Mg2+) and 2 nitrate ions 2(NO3-)

Chemical Formula: Mg(NO3)2(s)