Unit 5“Chemical Names

and Formulas”

ChemistryTroy High School

Mr. Blake

H2O

Section 9.1Naming Ions

Atoms and Ions• are

electrically neutral.–Same number of p+ and e-

• - atoms with a charge (+ or -)

• Made by gaining or losing .– Only electrons can move

An Anion is…• A negative ion =

electrons.• Nonmetals gain electrons.• Charge is written as a superscript on the right.

F1- Has gained electron (-ide is new ending = )

O2- Gained electrons ( )

A Cation is…• A positive ion =

electrons.• lose electrons

K1+ Has lost electron (no name change for positive ions)

Ca2+ Has lost electrons

Predicting Ionic ChargesGroup 1A:Lose electron to form ions

H1+ Li1+ Na1+ K1+ Rb1+

Predicting Ionic ChargesGroup 2A:Loses electrons to form ions

Be2+ Mg2+ Ca2+ Sr2+ Ba2+

Predicting Ionic ChargesGroup 3A: Loses electrons to form ions

B3+ Al3+ Ga3+

Predicting Ionic Charges

Group 4A: Do they lose 4 electrons or gain 4 electrons?

! Group 4A elements rarely form ions (they tend to share)

Predicting Ionic ChargesGroup 5A: Gains _ electrons to form ions

N3-

P3-

As3-

Nitride

Phosphide

Arsenide

Predicting Ionic ChargesGroup 6A: Gains electrons to form ions

O2-

S2-

Se2-

Oxide

Sulfide

Selenide

Predicting Ionic ChargesGroup 7A: Gains _ electron to form ions

F1-

Cl1-

Br1-Fluoride

Chloride

Bromide

I1-Iodide

Predicting Ionic ChargesGroup 8A: Stable noble gases

form ions!

Predicting Ionic ChargesGroup B elements: Many transition elements have possible charge.

Iron (II) = Iron (III) =

Use of Roman numerals to show charges

Naming Cations

• system – use roman numerals in parenthesis to indicate the charge value

Naming cations• If the charge is always the

(like in the Group A metals) just write the of the metal.– Calcium =

• metals can have more than one type of charge.– Indicate charge as roman numeral in

after the name of the metal (Table 9.2, p.255)

– Iron (IV) =

Predicting Ionic Charges Some elements also have more than one possible charge.Tin (II) = Lead ( ) = Pb2+

Tin (IV) = Lead ( ) = Pb 4+

Predicting Ionic ChargesGroup elements: Some transition elements have only one possible oxidation state, such as these three:

Zinc = Silver = Cadmium =

**Do not use roman numerals for these

Practice by naming these:• Na+ • Ca2+ • Al3+ • Fe3+ • Fe2+ • Pb2+ • Li+

Write symbols for these:

• Potassium ion• Magnesium ion • Copper (II) ion• Chromium (IV) ion• Barium ion• Mercury (II) ion

Naming Anions

• Anions are the same charge

• Change the ending to _

• F1- a Fluorine atom will become a ion.

Practice by naming these:

• Cl- • N3- • Br- • O2-

• Ga3+

Write symbols for these:

•Sulfide ion• Iodide ion•Phosphide ion•Strontium ion

Polyatomic ions are…• Groups of atoms that together,

have an charge, and one name.• Usually end in – or - _

• Acetate: C2H3O2-

• Nitr : NO3-

• Nitr : NO2-

• Permanganate: MnO4-

• Hydroxide: OH- and Cyanide: CN-?

• Sulf : SO42-

• Sulf : SO32-

• Carbonate: CO32-

• Chromate: CrO42-

• Dichromate: Cr2O72-

• Phosph : PO43-

• Phosph : PO33-

• Ammonium: NH41+

Know Table 9.3 on page 257

(One of the few positive polyatomic ions)

H + Polyatomic ion =….

•If the polyatomic ion begins with H, then put “hydrogen” in front of the polyatomic ion: H1+ + CO3

2- → HCO31-

hydrogen + carbonate → hydrogen carbonate ion

• HSO3

• HPO4

• HCO3

Helpful Hints on Oxy-Anions

1. _________: smaller # of oxygen2. _________: larger # of oxygen

Ex.

NO3- ____________________________

NO2- ____________________________

SO42- ____________________________

SO32- ____________________________

A Guide to Determine Whether the –ate Formula is –XO3 or –XO4:

B C N

Cl

Br

I

Si P S

As Se

1

2

3

4

5

6

1 2 13 14 15 16 17 18

Transition Metals

Section 9.2 Naming and Writing

Formulas for Ionic Compounds

Writing Ionic Compound FormulasExample: Iron (III) chloride

1. Write the cation and anion with CHARGES!

2. Balance charges using the criss-cross method with subscripts, if necessary. Use parentheses if you need more than one of a polyatomic ion to balance subscripts.

Writing Ionic Compound Formulas

Example: Aluminum sulfide

1. Write the cation and anion with CHARGES!

2. Balance charges using the criss-cross method with subscripts, if necessary. Use parentheses if you need more than one of a polyatomic ion to balance subscripts.

Writing Ionic Compound Formulas

Example: Zinc hydroxide

1. Write the cation and anion with CHARGES!

2. Balance charges using the criss-cross method with subscripts, if necessary. Use parentheses if you need more than one of a polyatomic ion to balance subscripts.

Writing Ionic Compound Formulas

Example: Magnesium carbonate (note the 2 word name)

1. Write the formulas for the cation and anion, including CHARGES!

Mg2+CO32-

2. Check to see if charges are balanced.

They are balanced!

Writing Ionic Compound Formulas

Example: Barium nitrate (note the 2 word name)1. Write the cation and anion with CHARGES!

2. Balance charges using the criss-cross method with subscripts, if necessary. Use parentheses if you need more than one of a polyatomic ion to balance subscripts.

Writing Ionic Compound FormulasExample: Ammonium sulfate

1. Write the cation and anion with CHARGES!

2. Balance charges using the criss-cross method with subscripts, if necessary. Use parentheses if you need more than one of a polyatomic ion to balance subscripts.

Writing Ionic Compound Formulas

Example: Aluminum phosphate

1. Write the formulas for the cation and anion, including CHARGES!

Al3+ PO43-

2. Check to see if charges are balanced.

They ARE balanced!

Naming Ionic Compounds• 1. Cation , then anion

• 2. Monatomic cation = name of the element

• Ca2+ = ion

• 3. Monatomic anion = root + -ide

• Cl- =

• CaCl2 =

Naming Ionic Compounds

• If the metal can have more than one charge ( ), use a Roman numeral in their name:

PbCl2 use the to find the

charge on the cation (chloride is always 1-)

(Metals with multiple oxidation states)

is the lead ( ) cation

PbCl2 = lead ( ) chloride

Things to look for:

1) If cations have ( ), the number in parenthesis is their

.2) If anions end in –ide, they are

probably off the periodic table

( )3) If anion ends in -ate or –ite,

then it is

Practice by writing the formula or name as required…

• Iron (II) Phosphate• Stannous Fluoride• Potassium Sulfide• Ammonium

Chromate• MgSO4

• FeCl3

Section 9.3Naming and Writing

Formulas for Molecular

Compounds

Molecular compounds are…• Made of only

• Smallest part is a • Can’t use charges to figure

out how many of each atom (there are no charges present / they share electrons)

Molecular compounds are easier!• compounds use

to determine how many of each.• Figure out charges and criss-cross numbers.

• Molecular compounds: the name tells you the number of atoms.• Uses to tell you

the exact number of each element present!

Prefixes (Table 9.4, p.269)

• 1 = mono-• 2 = di-• 3 = • 4 = tetra-• 5 = • 6 = hexa-• 7 = hepta-• 8 = octa-

• 9 = nona-• 10 =

Prefixes• To write the name, include:

• One exception is we don’t write if there is only of

the element.• Normally, we do not have double vowels

when writing names (oa oo)

Prefix + name -ide

Practice by naming these:

• N2O

• NO2

• Cl2O7

• CBr4

• CO2

• BaCl2

Write formulas for these:• diphosphorus

pentoxide• tetraiodine nonoxide• sulfur hexafluoride• nitrogen trioxide• carbon tetrahydride• phosphorus trifluoride• aluminum chloride(Ionic compound)

Section 9.4Naming and Writing Formulas for Acids

and Bases

Acids are…• Compounds that give off

ions (H+) when dissolved in water (the Arrhenius definition)

• Formula starts with .• Always be some Hydrogen

next to an .• determines the

name.

Rules for Naming acids: Name it as a normal compound first

• If the anion attached to hydrogen ends in -ide, put the prefix and change -ide to - acid

• In other words, if it’s just Hydrogen and one other nonmetal

• HCl = • H2S =

acid

acid

Naming Acids• If the anion has oxygen in it, then it ends

in -ate or -ite2) Change -ate to -ic acid (use no prefix)

• Example: HNO3 Hydrogen + nitrate =

3) Change -ite to -ous acid (use no prefix)• Example: HNO2 Hydrogen + nitrite

=

Naming Acids

Normal ending

____-ide

____-ate

____-ite

Acid name is…

hydro-___-ic acid

_____-ic acid

_____-ous acid

Practice by naming these:

• HF• H3P

• H2SO4

• H2SO3 • HCN• H3PO4

Writing Acid Formulas – in reverse!• Hydrogen will be listed first• The name will tell you the • Be sure the charges cancel out.

• Starts with hydro?• Anion is

, ends in –ide

• No hydro?1) -ate anion

comes from – ending

2) -ite anion comes from – ending

Write formulas for these:

• hydroiodic acid• chloric acid• carbonic acid• phosphorous acid• hydrobromic acid

Names and Formulas for Bases

• Base - an ionic compound that produces ions ( ) when dissolved in water (the Arrhenius definition)

• Named the same way as other ionic compounds:–Name of cation ( ) followed by

name of anion (which will be ).

Names and Formulas for Bases

• NaOH =• Ca(OH)2 =

• To write the formula:

1) Write symbol for metal cation

2) Followed by hydroxide ion (OH1-)

3) Use criss-cross method to balance the charges.

Practice by writing the formula for the following:

• Magnesium hydroxide• Iron (III) hydroxide• Zinc hydroxide

Section 9.5The Laws Governing

Formulas and Names

Some Laws:

Law of Proportions- in a sample of a chemical compound, the of the

are always in the proportions.

In every molecule of H2O (water), the mass ratio of H:O is 1:8

Some Laws:Law of Proportions- Whenever two elements form than one compound, the masses of one element that combine with the mass of the other element are in the ratio of small .

H2O (water) and H2O2 (hydrogen peroxide)

2:1 2:2

2g:16g 2g:32g

• https://www.youtube.com/watch?v=0OOcpiTiXzM

• Law of Definite Proportions - Law of Multiple Proportions

• by Brightstorm

Summary of Naming and Formula Writing

• For naming, follow the flowchart- Figure 9.20, page 277

• For writing formulas, follow the flowchart from Figure 9.22, page 278

Helpful to remember...1. In ionic compounds, the net charge is

_ (criss-cross method)2. Put -ide at the end of monatomic

3. An -ite or -ate ending means there is a ion that

has 4. Prefixes generally mean ;

they show the number of each atom

Helpful to remember...5. A Roman numeral after the name

of a cation is the of the cation