writing chemical formulas and naming chemical compounds

Writing Chemical Formulas and Naming Chemical Compounds

Lesson #5 – Naming Metal-Non-Metal Compounds

• Words for your glossary:• Chemical Formula• Valence• Binary Compound • Zero Sum Rule• Polyatomic Ion

The Language of Chemistry

http://www.youtube.com/watch?v=q2s8hQ5NIpE&feature=related• It’s like learning a new language• You will learn to take the name of a compound and

then find it’s formula Eg. Carbon dioxide = CO2

• You will also learn to translate a formula into words Eg. MgCl2 becomes magnesium chloride.

• There are three main patterns: naming ionic compounds, polyatomic ions, and covalent compounds.

Chemical Formulas

• Provides two important types of information:• 1.

________________________________________________________________

• 2. The number of atoms of each element that are present in a compound.

• Tip: __________________________________________________

• Eg. Ca + Br (pp.95 in text)

What a chemical formula represents

• In covalent compounds: how many of each type of atom are in the molecule

• Eg. NH3

• In Ionic compounds: ______________________________________________

• Eg. MgO• Remember that ionic

compounds are found in a lattice structure so in MgO, the atoms exist in a 1:1 ratio, held together by ionic bonds.

Valence Numbers

• Valence: __________________________________________________________________________________________________

• Eg. Group 1 elements have the capacity to lose one e- in order to bond. They have a valence of +1.

• Some larger elements have 2 or more valence numbers. Table 3.3, pp. 97.

Naming Compounds That Contain a Metal and a Nonmetal

• Binary ionic compounds contain ___________• _____________________________________

– Type I compounds • Metal present forms only one cation

– Type II compounds • Metal present can form 2 or more cations with different charges

Naming Compounds That Contain a Metal and a Nonmetal

Naming Ionic Compounds

Type I Binary Ionic compounds

Naming Compounds That Contain a Metal and a Nonmetal

• For compounds containing both a metal and a nonmetal, ____________________________The nonmetal is named from the root element name.

Cations with 2 or more Valences

Type II Binary Ionic compounds • Since the metal ion can have more than one charge, a

________________________is used to specify the charge. • Outlined in your text as the Stock System (pp.103, table 3.6)

Common multi-valent cations

Type II Binary Ionic compounds

• Polyatomic ions are charged entities composed of several atoms bound together.

• They have special names and must be memorized.

Polyatomic Ions YOU need to know

• Chlorate• Nitrate• Carbonate• Sulfate• Phosphate • Ammonium• Hydroxide

• Naming ionic compounds containing polyatomic ions follows rules similar to those for binary compounds. – ammonium acetate

Polyatomic Ions

• ____________________________________• “poly” means “many” or “lots” in Greek• __________________________________• Remain unchanged in simple reactions because of

_________________________• They behave like a single unit and should be

treated as a ______________________• The most common is NH4

+ - Ammonium• Table 3.4 pp. 98

Writing Chemical Formulas Using Valences

• Zero Sum Rule:

• Eg. KF = the sum of the valences is O• What if you have compound that has multi-

valent ions?

Cross-Over Rule

• Cross Over Rule lets you balance the equations. Pp.99 in your text.

• Let’s take Mg – Cl• 1. Write the unbalanced formula (metals first)• 2. Add the valence numbers• 3. Cross over numbers• 4. Check the subscripts (reduce or remove any

valences of 1)

Practice!

• Sodium Sulphide • Aluminum Sulphide• Calcium Oxide• Calcium Phosphide

Crossing Over with Polyatomic Ions

• Metal + Polyatomic Ion:• Eg. K – PO4 (potassium phosphate)• 1. Write unbalanced formula. Put brackets

around the polyatomic ion (s)• 2. Write in the valences• 3. Cross over, write in the subscripts• 4. Tidy up: get rid of 1s, if needed, get rid of

the brackets.

Poly on Poly

• Try Ammonium Phosphate!What about Ammonium Sulphate?

Putting it all together

• To name a binary compound (2 elements) which is ionic, write the metal first and the non-metal ending in –ide

• Eg. Potassium Bromide• If there is an alternate valence, use the stock

system when naming the compound.• Eg. Lead (II) oxide (Pb2+ + O)• Conversely, use the cross over rule to find the

chemical formula of a compound.

One side note….Naming compounds that contain

Hydrogen• Can be the first name / least EN• Eg. HCI – Hydrogen chloride • OR can be more EN• Eg. Sodium hydride or lithium hydride. • Many compounds that contain H are acids. We

will discuss this later………..

Copy the following table and fill in the correct formula or name for each of the compounds listed:

FORMULA NAME

Al2O3

MgBr2

Potassium oxide

Ag2S

Manganese ( VII) oxide

PbCl2

Calcium oxide

Copper (II) chloride

BaCl2

Ferric Phosphide

Lesson #6 – Naming compounds with polyatomic ions

Pattern!

• ClO- : hypochlorate• ClO2

- : chlorite

• ClO3- : chlorate

• ClO4- : perchlorate

• Can YOU see it?

Table 3.7 – Meaning of prefixes and suffixes (pp.105)

Prefix and Suffix Number of oxygen atoms

HYPO ___________________ITE

X -2 OXYGEN ATOMS

___________________ITE

X-1 OXYGEN ATOMS

___________________ATE

X OXYGEN ATOMS

PER ___________________ATE

X+1 OXYGEN ATOMS

Really? Yes, Really!

• http://www.youtube.com/watch?v=Jp5yblKmQQI&feature=related

Practice, Practice, Practice!!

• Let’s do #23 on pp. 105 together!• Make sure you do the homework for these

two lessons. The only way to be good at this stuff is to do LOTS of examples!

• Pp. 19 in your green book!• Make sure you do your readings for lessons

6&7 for Monday!