Chapter 6. Chemical Names and Formulas
An Anion
* A negative ion. * Has gained electrons
Rules for Naming Anions
* Anions are always the same charge * Change the monatomic element ending to - ide
Ion
* Charged atom or group of atoms (cation or anion) * Cation name: same name + "ion" (Na+ is called "sodium ion") * Anion name: root name ends with "-ide" (Cl- is called "chloride")
Chemical Formula
* Shows kinds (symbol) and numbers (subscript) of atoms, i.e. composition * Gives NO information regarding structure
F
F-
Rb
Rb+
C2H3O2 -
Acetate
Al
Al3+
metal cations with more than one charge: Classical name
uses root word with suffixes (-ous for lower and -ic for higher charge)
Law of Multiple Proportions
when two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.
HSO3 -
Hydrogen sulfite
Rules for Naming Ionic Compounds
1. Name the cation first, then anion 2. Monatomic cation = name of the element 3. Monatomic anion = root + -ide
Be
Be2+
Br
Br-
Ca
Ca2+
CO3 2-
Carbonate
Ionic Compound
Composed of metal cation and nonmetal anion
Cu +
Copper (I) ion Curpous ion
Cu 2+
Copper (II) ion Cupric ion
Cs
Cs+
CN -
Cyanide
Prefixes: 3
tri-
metal cations with more than one charge: Stock name
uses roman numerals in parenthesis to indicate the actual charge
Acids are
* Compounds that give off hydrogen ions (H1+) when dissolved in water (the Arrhenius definition) * Will start the formula with H. * There will always be some Hydrogen next to an anion. * The anion determines the name.
Polyatomic ions
* Groups of atoms that stay together and have an overall charge, and one name. * Usually end in -ate or -ite * Acetate: C2H3O2 1- * Nitrate: NO3 1- * Nitrite: NO2 1- * Permanganate: MnO4 1- * Hydroxide: OH 1- * Cyanide: CN 1-
Writing Acid Formulas - in reverse
* Hydrogen will be listed first * The name will tell you the anion * Be sure the charges cancel out. * Starts with prefix hydro?- there is no oxygen, * -ide ending for anion * no prefix hydro * -ate anion comes from -ic ending * -ite anion comes from -ous ending
molecule
* Neutral chemically bonded group of atoms that act as a unit * Usually composed of 2 or more nonmetal atoms * Make up molecular compounds
Rules for Naming acids
1. Name it as a normal compound first. If the anion attached to hydrogen ends in -ide, put the prefix hydro- and change -ide to -ic acid 2. If the anion has oxygen in it, then it ends in -ate or -ite 3. change the suffix -ate to -ic acid (use no prefix) 4. change the suffix -ite to -ous acid (use no prefix) 5. If the acid has 1 more oxygen than the -ic acid, add the prefix per- 6. If there is 1 less oxygen than the -ous acid, add the prefix hypo-
Steps for Writing Ionic Compound Formulas
1. Write the formulas for the cation and anion, including CHARGES! 2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Use the criss-cross method to balance subscripts.
Rules for Naming Ionic Compounds: Metals with multiple oxidation states
1. some metals can form more than one charge (usually the transition metals) 2. use a Roman numeral in their name: 3. use the anion to find the charge on the cation
Naming Acids: Normal compound ending ___-ate changes to
Acid name: ____-ic acid
Naming Acids: Normal compound ending ___-ite changes to
Acid name: ____-ous acid
Naming Acids: Normal compound ending ___-ide changes to
Acid name: hydro-____-ic acid
NH4 +
Ammonium
As
As3-
Ba
Ba2+
ClO3 -
Chlorate
ClO2 -
Chlorite
CrO4 2-
Chromate
Cr 2+
Chromium (II) ion Chromous ion
Cr 3+
Chromium (III) ion Chromic ion
Cl
Cl-
Co 2+
Cobalt (II) ion Cobaltous ion
Co 3+
Cobalt (III) ion Cobaltic ion
Cr2O7 2-
Dichromate
H2PO4 -
Dihydrogen Phosphate
Naming Exceptions: transition metals that have only one ionic charge
Do not use roman numerals for these: * Silver is always 1+ (Ag1+) * Cadmium and Zinc are always 2+ (Cd2+ and Zn2+)
HPO4 2-
Hydrogen Phosphate
HCO3 -
Hydrogen sulfate
OH -
Hydroxide
ClO -
Hypochlorite
I
I-
Fe 2+
Iron (II) ion Ferrous ion
Fe 3+
Iron (III) ion Ferric ion
K
K+
Pb 2+
Lead (II) ion Plumbous ion
Pb 4+
Lead (IV) ion Plumbic ion
Li
Li+
Mn 2+
Manganese (II) ion Manganous ion
Mn 3+
Manganese (III) ion Manganic ion
Hg2 2+
Mercury (I) ion Mercurous ion a diatomic elemental ion
Hg 2+
Mercury (II) ion Mercuric ion
Mg
Mg2+
N
N3-
Na
Na+
NO3 -
Nitrate
NO2 -
Nitrite
O
O2-
C2O4 2-
Oxalate
P
P3-
ClO4 -
Perchlorate
MnO4 -
Permanganate
PO4 3-
Phosphate
PO3 3-
Phosphite
Oxyanions
Polyatomic anions that contain oxygen
S
S2-
Se
Se2-
SiO3 2-
Silicate
Sr
Sr2+
SO4 2-
Sulfate
SO3 2-
Sulfite
Sn 2+
Tin (II) ion Stannous ion
Sn 4+
Tin (IV) ion Stannic ion
Nonmetals
can gain electrons
Prefixes: 10
deca-
Prefixes: 2
di-
Prefixes: 7
hepta-
Prefixes: 6
hexa-
Law of Definite Proportions
in a sample of any chemical compound, the masses of the elements are always in the same proportions.
Prefixes: 1
mono- Exception: we don't write mono if there is only one of the first element.
Prefixes: 9
nona-
Prefixes: 8
octa-
Prefixes: 5
penta-
Formula unit
represents an ionic compound, lowest whole number ratio
Molecular formula
represents molecular compound
Prefixes: 4
tetra-
