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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!