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Unit 05. Chemical Nomenclature. Key Vocabulary. IUPAC - I nternational U nion of P ure and A pplied C hemistry Responsible for chemical naming worldwide Rules for naming and writing compounds - PowerPoint PPT Presentation
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CHEMICAL NOMENCLATURE
Unit 05
Key Vocabulary
IUPAC - International Union of Pure and Applied Chemistry Responsible for chemical naming worldwide Rules for naming and writing compounds
Law of Definite Proportions – states that in samples of any chemical compound, the masses of the elements are always in the same proportions.
Chemical Formula - Symbols for its constituent elements are used; also shows number of atoms present in smallest representative unit of the substance.
Key Vocabulary
Oxidation Number – A measure of the charge of an atom if the electrons shared in bonding were held only by the more electronegative atom.
For example, in water (H2O), oxygen is more electronegative than hydrogen. This would give oxygen all the electrons and an oxidation number of -2 and each hydrogen an oxidation number of +1.
For simple atoms or ions, the oxidation number is equal to the ionic charge.
For a neutral element like Helium (He), the oxidation number is 0.
Key Vocabulary
Acid – compound that produces hydrogen ions (H+) in solution.
Base – compound that produces hydroxide ions (OH-) in solution.
Monatomic ion – a single atom with a + or – charge as a result of losing or gaining valence electrons. Examples: Na + Al 3+ P 3- Br
1-
Polyatomic ion – a tightly bound group of atoms that behaves as a unit and carries a charge. Examples: NH4
+ NO3- OH - SO4
2-
Transition Metals
Many of the cations of transition metals have more than one common ionic charge. Examples - cations of Iron: Fe 2+ and Fe 3+
This is also true for tin (Sn) and lead(Pb), the two metals in group 4A.
Use the stock system to name theseStock system – as part of the name of the
element, a Roman numeral in parentheses indicates the value of the charge. Example: Fe 2+ = Iron (II) and Fe 3+ = Iron (III) See page 144 in textbook, table 6.3 for more examples
Naming Simple Ionic Compounds
Ionic Compound = cation + anion
1. write the name of the cation (metal) If transition metal, useRoman numeral in parentheses
• Example: Iron(II)
2. write the anion(nonmetal)—change ending to –ide
Ex. NaCl cation = Sodiumanion = Chlorine
Name = Sodium chloride
Practice
CaI2 Calcium iodide
LiF Lithium fluoride
MgOMagnesium oxide
BeF2 Beryllium fluoride
FeCl2 Iron (II) chloride
Naming Ionic Compounds with Polyatomics
Polyatomic ion review 1. write the name of the cation (metal)
If transition metal, may need Roman numeral in parentheses
2. write the polyatomic ion— see common ones on your STAAR reference materials.
Special note: NH4+ is the only positive polyatomic
ion
See pp. 146-147 in textbook, table 6.4
Practice
Na2SO4 Sodium sulfate
CaCO3 Calcium carbonate
Li3PO3 Lithium phosphite
NH4Cl Ammonium chloride
Writing Ionic Formulas
Criss Cross Method 1. write chemical symbol for each element or
polyatomic
2. find the charge for each element or polyatomic (Transition metal—look at the roman numeral)
3. criss cross the charges to the opposite subscript
Notes: if charges can be reduced, do so before crossing down Use parentheses for polyatomics
Practice
Lithium fluoride LiF
Calcium sulfide CaS
Iron (III) chloride FeCl3
Potassium nitride K3N
Practice with polyatomics
Ammonium chloride NH4Cl
Sodium sulfate Na2SO4
Magnesium carbonate MgCO3
Naming Covalent Compounds
Covalent compound review
No charges
Share electrons
2 or more nonmetals
Examples: CO2, H2O, SF2
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Use prefixes to designate the subscriptPrefix Number
Mono 1
Di 2
Tri 3
Tetra 4
Penta 5
Hexa 6
Hepta 7
Octa 8
Nona 9
Deca 10
CO2
Carbon dioxide
Notes: the second element still takes the –ide ending Do not use mono for the first element
Practice
S2O4 Disulfur tetroxide
FCl3 Fluorine trichloride
N2O Dinitrogen monoxide
NO2 Nitrogen dioxide
Writing covalent formulas
Write the element symbol and add the prefix as subscript DO NOT CRISS CROSS …PREFIX STAYS WITH
ORIGINAL ELEMENT
Sulfur trioxide
Dinitrogen tetrafluoride
Hexasulfur pentaiodide