Naming and WritingFormulas

for Compounds

Ionic Compounds

• Two Systems

1.Stock (Roman numerals)

2.Old

Stock System• Binary Compounds1. Write the name of

the positive ion 1st

2. Check to see if it has more than one oxidation #-if it does determine the charge and use a Roman numeral to designate the charge

3. Write the root name of the negative ion-add the ending -ide

• Compounds with Polyatomic ions

1. Same steps as binary for positive ion

2. For negative ion, just write the name of the polyatomic

DO NOT ADD THE ENDING -IDE

Determining Charge for Ions w/ Varible Oxidation #’s

• Ions w/ more than one oxidation #

1. Hg2. Cu3. Pb4. Sn5. Cr6. Fe

• Assign an oxidation # to the negative ion

Ex. Hg Cl-1

Multiply the oxidation # by the subscriptEx. Hg Cl-1 1

Since the compound is neutral the overall charge must = 0

Ex. Hg+1 Cl-1 = 0 1 1

+1-1 = 0

Remember…. Roman numerals are only used for those ions with more than

one charge!!!!!!!!

1. Sodium Chloride

2. Strontium chloride

3. Sodium hydroxide

4. Copper (II) chloride

5. Lead (IV) oxide

6. Copper (I) hydroxide

7. Mercury (II) bromide

8. Aluminum oxide

9. Strontium oxide

10. Mercury (II) oxide

1. NaCl2. SrCl23. NaOH4. CuCl25. PbO2

6. CuOH7. HgBr2

8. Al2O3

9. SrO10.HgO

Old System

1. Write the name of the positive ion 1st-check to see if the ion has more than one oxidation #-if it does, determine the charge and add one of the following endings

a) –ous for lowerb) -ic for higher

Remember…-ous is less-ic is more

2. Write the root of the negative ion

3. Add –ide if it is an element

4. Write the name of the ion if it is a polyatomic

Old System Names

• Cu +1cuprous

• Hg+1 mercurous

• Fe+2 ferrous

• Pb+2 plumbous

• Sn+2 stannous

• Cu+2 cupric

• Hg+2 mercuric

• Fe+3 ferric

• Pb+4 plumbic

• Sn+4 stannic

1. Hg(OH)2

2. SnCl23. PbO

4. CuCl

5. FeO

6. Fe2O3

7. HgOH

1. Mercuric hydroxide

2. Stannous chloride

3. Plumbous oxide

4. Cuprous chloride

5. Ferrous oxide

6. Ferric oxide

7. Mercurous hydroxide

1. Write the symbols for the ions side by side, with the positive ion 1st

2. Cross over charges diagonally to give subscripts

(Subscripts tell how many of each element are in the compound).

3. Check the subscripts to make sure the compound is neutral.

4. Do not write subscripts that are 1 (they are understood)

5. Do not write subscripts that are the same #6. If the subscripts are divisible by the same #,

reduce them to give the simplest ratio7. If the compound contains a polyatomic ion that

will have a subscript from crossing over, you must PUT PARENTHESIS AROUND IT!!!!

Examples

Write the formula for:

Strontium Chloride

1. Sr+2 Cl -1

2. SrCl2

**subscripts that are 1

are not written

• Write the formula for:

Magnesium Oxide

1. Mg +2 O-2

2. MgO

** subscripts that are the same # are not written

More Examples• Write the formula for:

Lead (IV) oxide** remember, the Roman numeral

tells you the oxidation #

Pb+4 O-2

Pb2O4 (these can be reduced)

PbO2

• Write the formula for:

Stannic sulfate

Sn +4 SO4-2

(the –ic ending tells you that it is tin’s higher charge)

Sn(SO4)2

** the subscripts can be reduced and sulfate must have parenthesis because it is a polyatomic ion and it has a subscript that will be written

Write the formulas for:

• Lithium bromide• Strontium sulfide• Aluminum oxide• Mercury (II) hydroxide• Plumbic carbonate• Ferrous oxide• Ferric oxide• Ammonium sulfate

• ONLY USED FOR NAMING COVALENTLY BONDED COMPOUNDS

(Remember… this will be two nonmetals bonded together)

• Write the name of the least electronegative element 1st.

• A prefix is used w/the name of the 1st element only if more than one atom is present

• The second element always get a prefix

• Then write the root and add -ide

Numerical Prefixes for Binary Molecular

Number Prefix

1 Mono

2 Di

3 Tri

4 Tetra

5 Penta

6 Hexa

7 Hepta

8 Octa

9 Nona

10 Deca

Examples

•Name:

1. N2ODinitrogen monoxide2. NONitrogen monoxide

3. N2O3

Dinitrogen trioxide

Writing Formulas for Binary Molecular

• Use the prefixes to tell you how many of each element is in the compound.

• Examples:

1. Disulfur trioxide

S2O3

2. Carbon monoxide

CO

3. Carbon tetrachloride

CCl4

Recognizing Acids

• At this very beginning level, you will recognize an acid by the fact that its formula starts with H, as in these examples:

• HClHNO3

H2SO4

HClO3

H3BO3

The name of an acid is derived from its anion:

• For acids in which the anion is an element, the name of the acid begins with the

prefix –hydro

• The acids name also includes the root name of the anion and the word acid

• In addition, you must change the suffix of the anion to -ic

• For acids in which the anion is a polyatomic, the prefix -hydro IS NOT USED!!!

• Write the name of the polyatomic and:

Change –ate to –icAnd -ite to -ous• Then write the

word acid.

•Name the following acids:

• 1) H3PO4

• 2) H2CO3

• 3) H2SO4

• 4) HIO3

• 5) HF

• 6) HNO2

Remember… the prefix –hydro means its an element bonded with hydrogen, no –hydro

means it’s a polyatomic

Write the formula for these acids:• hydrobromic acid• nitric acid• sulfurous acid• phosphorous acid• acetic acid