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Remember:
Molecules are substances that are covalently bonded together.
They contain a nonmetal bonded to a nonmetal.
How can you tell the difference between a polyatomic ion and a molecule?
Poly-ions have a charge when not bonded to a metal – ex. (PO
4
) 3or K
3
PO
4
Molecules contain only nonmetals and
NO overall charge – ex. P
2
O
3
In order to be effective in naming molecules, these prefixes must be committed to memory:
1 mono6 hexa-
2 di-
3 tri-
4 tetra-
7 hepta-
8 octa-
9 nona-
5 penta10 deca-
2
6
EX: SO
3 is ____________________
Sulfur trioxide
PBr
5 is ____________________
Phosphorus pentabromide
ICl
3 is _____________________
Iodine trichloride
H
2
0 is _____________________
Dihydrogen monoxide
Now… let’s look at writing the molecular formula from the name.
When writing the formula of a molecule, an atom’s prefix is its subscript.
Do not cross anything.
When there is only one of the first atom, a prefix is not used.
Let’s view some examples…
Names to Formulas
1. Write symbols of elements
2. Write number of atoms
tri
ide
SO
3
Final Formula implied and not written
Names to Formulas di
hept
ide
1. Write symbols of elements
2. Write number of atoms
Final Formula
Names to Formulas
ide
1. Write symbols of elements
2. Write number of atoms
PCl
5
If no prefix, then
1 is implied and not written
Names to Formulas
mon
ide
1. Write symbols of elements
2. Write number of atoms
If no prefix, then
1 is implied and not written
Names to Formulas
ide
1. Write symbols of elements
2. Write number of atoms
C O
1 is implied and not written
Names to Formulas di nitrogen tri sulf ide
1. Write symbols of elements
2. Write number of atoms
Final Formula
ANOL
BUTANOL
MORONIC ACID
CRAPINON
Exactly four water molecules and one hydrogen chloride molecule are necessary to form the smallest droplet of acid
Acids are molecular compounds that contain hydrogen bonded to a nonmetal or to a group of polyatomic ions.
Acids can be either binary or ternary compounds.
Names of binary acids have the form hydro-…ic acid.
Names of ternary acids use a series of prefixes and suffixes to specify the # of oxygen atoms in the molecule.
hydrochloric acid
Names of binary acids have the form hydro-…ic acid
EX: Binary acid: HF is hydrofluoric acid
HCl is hydrochloric acid
Try:
H
2
S i s _____________________
Hydrosulfuric acid
HI is _____________________
Hydroiodic acid
HBr is _____________________
Hydrobromic acid
When naming ternary acids, identify polyatomic ion in the formula.
For polyions that end in “ate” change the ending to “ic”.
(Something I “ate” made me feel “ic”.)
For polyions that end in “ite” change the ending to “ous”.
(A snake b“ite” is poison“ous”)
EX: nitrate nitric nitrite nitrous sulfite sulfous sulfate sulfic
Some ternary acids have more than one oxygen possibility.
When naming ternary acids from polyions that have up to four oxygen possibilities: per-… -ic greatest # of oxygen atoms.
-ic greater
-ous smaller hypo-… -ous smallest # of oxygen atoms.
*Know all forms of ClO
3
-1 and IO
3
-1
Polyion Acid Formula Acid Name
ClO
ClO
ClO
4
-1
3
-1
2
-1
ClO -1
HClO
HClO
HClO
HClO
4
3
2 perchloric acid chloric acid chlorous acid hypochlorous acid
Name:
HIO
Hypoiodous acid
HIO
2
Iodous acid
HIO
3
Iodic acid
HIO
4
Periodic acid
EX: HCl is ____________________
Hydrochloric acid
H
2
SO
4 is ____________________
Sulfuric acid
H
3
PO
4 is _____________________
Phosphoric acid
HF is _____________________
Hydroflouric acid
HNO
3 is _____________________
Nitric acid
HNO
2 is _____________________
Nitrous acid
Acids are molecules that are covalently bonded yet they have properties of ionic compounds so use rules for creating neutral ionic compounds.
Formulas for acids begin with Hydrogen. The oxidation state for hydrogen is +1.
Identify if the acid is binary or ternary. If the acid is binary, it will have a “hydro” prefix, all others will be ternary.
Write H +1
Identify the monotomic anion by its root name in the acid.
Determine its charge by following the oxidation trend for the groups.
Write the element symbol and its negative oxidation.
Criss Cross charges to create neutral acid formulas.
EX: hydrosulfuric acid
H +1 S -2
H
2
S
Now Try: hydrochloric acid hydrobromic acid hydrophosphoric acid hydrofluoric acid
H + + Cl = HCl
H + + Br = HBr
H + + P -3 = H
3
P
H + + F = HF
Write H +1
Identify polyion by:
1. ic ate and ous ite suffixes
2. prefixes of per and hypo to indicate numbers of oxygen atoms for chlorates and iodates.
Write formula of polyion including oxidation.
Criss Cross charges for neutral formula.
EX: sulfuric acid
H +1 SO
4
-2
H
2
SO
4
Now try: phosphoric acid
(ate to ic) H + + PO
4
-3 nitrous acid
(ite to ous) H + + NO
2
perchloric acid
= H
3
PO
4
= HNO
2
(ate to ic) H + + ClO
4
acetic acid
= HClO
4
(ate to ic) H + + C
2
H
3
O
2
= HC
2
H
3
O
2 nitric acid
(ate to ic) H + + NO
3
sulfurous acid
(ite to ous) H + + SO
3
-2 hypoiodous acid
H + + IO = HIO
= HNO
3
= H
2
SO
3
1. Ionic Compounds
Binary Ionic Compounds
Ionic Compounds with Polyatomic Ions
Oxidation #s must add to zero (criss cross)
Some elements have more than one oxidation #
Metal & Non-metal
2. Molecular Compounds
Binary Molecular Compounds
Non-metal & non-metal
Use prefixes
3. Acids
Binary Acids
Acids with Polyatomic Ions
Hydrogen in front of elements
Oxidation #s must add to zero (criss cross)
4. NAMING COMPOUNDS
Hint … identify the first element… if it is…
METAL – know it is an IONIC COMPOUND
(think oxidation# & criss cross)
NON-METAL – know it is a MOLECULAR COMPOUND
( think prefixes)
HYDROGEN – know it is an ACID
(think oxidation# & criss cross… or ate/ic & ite/ous)