Unit 12: Writing and Naming Chemical Formulas

Physical Science

Chemical Symbols

How to writing chemical formulas

Use the chemical symbol for each element

Usually, the element abbreviations come from the word

(He for Helium or Ti for Titanium)

Some elements have just one letter, such as H for Hydrogen or N for Nitrogen

How to writing chemical formulas

Sometimes the abbreviation does not look like the element such as:

K for PotassiumNa for SodiumPb for LeadCu for Copper Ag for SilverAu for Gold

How to writing chemical formulas

That is because their name came from Latin or other languages

K for Potassium (Kalium)Na for Sodium (Natrium)Pb for Lead (Plumbum)Cu for Copper (Cuprum)Ag for Silver (Argentum)Au for Gold (Aurum)

The 11 Odd Elements to Memorize

How to writing chemical formulas

Most elements have two letters Always capitalize the first letter and

use lower case on the second one.Example: Cobalt is Co

If you used two capitals (CO), it would be mistaken for Carbon Monoxide which has one Carbon (C) and one Oxygen (O)

Subscript Numbers

The subscript number specifies how many atoms of that element you have

N2 is a nitrogen molecule with two atoms

C2H4 has two carbons and four hydrogens.

CO2 is carbon dioxide and contains one carbon and two oxygens

If no number is listed, it means there is only one

More Examples

C2H3Cl what elements and how many of each?

More Examples

C2H3Cl what elements and how many of each?

More Examples

H2SiCl2what elements and how many of each?

More Examples

H2SiCl2what elements and how many of each?

Numbers in Front Versus Behind

What should this molecule look like?

For example CH4 =

Numbers in Front Versus Behind

What should this molecule look like? It is called Methane For example CH4 =

Numbers in Front

When there are large numbers in front, that tells you how many molecules there are.

For example 3CH4 =

Numbers in Front

When there are large numbers in front, that tells you how many molecules there are.

For example 3CH4 = 3 methane molecules

12NaOH = ?

Numbers in Front

When there are large numbers in front, that tells you how many molecules there are.

For example 3CH4 = 3 methane molecules

12NaOH = 12 different Sodium Hydroxide molecules.

Part One: Ionic Formulas

Part One: Writing Ionic Formulas

Always say the metal name first and then the non-metal with an -ide

Part One: Ionic Formulas

Part One: Writing Ionic Formulas

Example: CaCl2 would be called calcium chloride

Part One: Ionic Formulas

Part One: Writing Ionic Formulas

Example: What if you saw the name Magnesium chloride …What is the formula?

Part One: Ionic Formulas

Magnesium Chloride =

Mg+2 Cl-1

Part One: Ionic Formulas

Magnesium Chloride = MgCl2

Mg+2 Cl-1

Part One: Ionic Formulas

OK, here is one for you Magnesium Phosphate

Magnesium= Mg2+

Phosphate = PO43-

Remember, the charges have to balance

Part One: Ionic Formulas

OK, here is one for you Magnesium Phosphate

Magnesium= Mg2+

Phosphate = PO43-

Remember, the charges have to balance

2 X 3 = 6

Part One: Ionic Formulas

OK, here is one for you Magnesium Phosphate

Magnesium= Mg2+

Phosphate = PO43-

Remember, the charges have to balance

Mgx(PO4)y

+6 -6

2 X 3 = 6

Part One: Ionic Formulas

OK, here is one for you Magnesium Phosphate

Magnesium= Mg2+

Phosphate = PO43-

Remember, the charges have to balance

Mg3(PO4)2

Examples of naming for metals with multiple charges

Element Cation Name Pronounced

copper Cu+ Copper (I) copper one

Cu2+

iron Fe2+ Iron (II) iron two

Fe3+

Lead Pb2+ Lead (II) lead two

Pb4+

Tin Sn2+ Tin (II) tin two

Sn4+

Examples of naming for metals with multiple charges

Element Cation Name Pronounced

copper Cu+ Copper (I) copper one

Cu2+ Copper (II) copper two

iron Fe2+ Iron (II) iron two

Fe3+ Iron (III) iron three

Lead Pb2+ Lead (II) lead two

Pb4+ Lead (IV) lead four

Tin Sn2+ Tin (II) tin two

Sn4+ Tin (IV) tin four

Part One: Ionic Formulas

What about Iron (II) Oxide

Step One: Determine the charges Iron (II) = Fe2+ and Oxide = O2-

Part One: Ionic Formulas

What about Iron (II) Oxide

Step One: Determine the charges Iron (II) = Fe2+ and Oxide = O2-

Step Two: See how to balance the charges

Step Three: Find the combination that balances

Part One: Ionic Formulas

What about Iron (II) Oxide

Step One: Determine the charges Iron (II) = Fe2+ and Oxide = O2-

Step Two: See how to balance the charges

Step Three: Find the combination that balances

Iron (II) Oxide = FeO

How do you know if you use Roman numerals? Do not use Roman Numerals for groups 1 or 2 as

they are always (+1) and (+2) accordingly.

K = +1 and Ca = +2+1

+2

How do you know if you use Roman numerals? Do not use Roman numerals for anything in the

P-block since they tend to form covalent bonds.

The exceptions are Tin (Sb) and Lead (Pb)

How do you know if you use Roman numerals? Do not use Roman numerals for Zn or Ag

because they have dominant oxidation states that rarely change:

Ag = +1 and Zn = +2.

Prefixes for Covalent Bonds

1 = Mono Carbon Monoxide (CO)Example

Prefixes for Covalent Bonds

1 = Mono Carbon Monoxide (CO)

2 = Di Carbon Dioxide (CO2)

Example

Prefixes for Covalent Bonds

1 = Mono Carbon Monoxide (CO)

2 = Di Carbon Dioxide (CO2)

3 = Tri Nitrogen Triiodide (NI3)

Example

As you can see, you don’t label the first with a prefix unless it is more than one

Prefixes for Covalent Bonds

1 = Mono Carbon Monoxide (CO)

2 = Di Carbon Dioxide (CO2)

3 = Tri Nitrogen Triiodide (NI3)

4 =Tetra Dinitrogen Tetroxide (N2O4)

Example

As you can see, you don’t label the first with a prefix unless it is more than one

Prefixes for Covalent Bonds

1 = Mono Carbon Monoxide (CO)

2 = Di Carbon Dioxide (CO2)

3 = Tri Nitrogen Triiodide (NI3)

4 =Tetra Dinitrogen Tetroxide (N2O4)

5 = Penta Phosphorus Pentachloride (PCl5)

Example

As you can see, you don’t label the first with a prefix unless it is more than one

Prefixes for Covalent Bonds

1 = Mono Carbon Monoxide (CO)

2 = Di Carbon Dioxide (CO2)

3 = Tri Nitrogen Triiodide (NI3)

4 =Tetra Dinitrogen Tetroxide (N2O4)

5 = Penta Phosphorus Pentachloride (PCl5)

6 = Hexa Sulfur Hexaflouride (SF6)

Example

As you can see, you don’t label the first with a prefix unless it is more than one

Drawing Covalent Compounds

In general, the first named compound is the central compound.

Sulfur dioxide

Nitrogen Triiodide

Carbon Tetrachloride