Download RULES OF CHEMICAL NOMENCLATURE I. Elements (periodic

RULES OF CHEMICAL NOMENCLATURE
I. Elements (periodic table)
A. Symbols: First letter or first two letters
of the elements name.
1. Some use latin name for symbol, ex.
gold (latin name= aurum or Au).
2. Learn all on page 166 that have an*
plus Sb, As, Bi, Ce, Cs, Au, Kr, Mo,Pt,
Ra, Rn, Rb, Sc, Se, Te, Tl, Ti, W, U &
Xe.
II.
Formula: Represents composition of a
compound.
A. Tells proportions of elements in a
compound relative to each other.
1. Subscripts are used to indicate
number of atoms of each element in
a compound. (whole numbers)
2. The subscript follows the atom or
atoms it refers to. If subscript
follows a “( )” then everything
inside the “( )” is multiplied by the
subscript.
B. All atoms have oxidation numbers
(valence). This is the combining power
of the atom.
C. Polyatomic ions or “radicals” are
groups of atoms that behave as if they
are single atoms. They also have
oxidation numbers. ( we will show
these later).
D. We will use the concept of valence to
write formulas.
1. Valence is either “+” or “-“.
2. In ALL compounds, the sum of the
valences adds up to zero.
3. Metals are always “+”.
4. Non-metals can be “+” or “-“.
5. Most radicals are “-“ , only common
“+” radical is NH4+1 (ammonium).
E. Atoms that have a constant valence
1. Always +1 (H, Li, Na, K, Rb, Cs,
Ag)
2. Always +2 ( Be, Mg, Ca, Sr, Ba,
Zn,Cd)
3. Always + 3 (Al)
(H can be –1 in some special cases)
III. Binary Salts: a compound of a metal and
a non-metal. (2 elements)
A. Metal is always written first
(because ‘+’ is always first), nonmetal is last.
B. Named by adding name of first
element (metal) to second element
(non-metal) whose name is modified
to end in “ide.” (metals are to the
left of the staircase; non-metals are
to the right in periodic table.)
(oxygen becomes “oxide,” chlorine
becomes “chloride,” sulfur becomes
“sulfide,” etc.)
C. Most metals have a variable valence
and this must be indicated in the
name of the compound.
1. The stock system: the valence (+)
of the metal is given as a Roman
numeral.
a. Iron (Fe) can be either Fe +2 or
Fe +3; therefore, both forms
exist in compounds. (ex. Iron
(II) Chloride = FeCl2 while
Iron (III) Chloride = FeCl3)
b. Can also be named Ferrous
Chloride and Ferric Chloride.
(This is the old way, but is
still valid).
IV. Salts: Those with Polyatomic ion or
“radical” (see radical sheet)
A. Four ways to identify salts:
1. metal + non-metal (binary)
2. metal + radical
3. radical (ammonium) + non-metal
4. radical (ammonium) + radical
B. Naming salts (other than binary)
1. name of metal plus name of
radical
2. name of radical (ammonium) plus
name of non-metal or other
radical.
C. The “common form” of the radical
must be memorized (see radical
sheet)
1. common form has “ate” ending
2. other endings are based on the
“ate” ending
a. if there is one less oxygen,
then the name ends in “ite”
b. if there are two less oxygen,
then the name starts with
“hypo” and ends in “ite”
c. if there is one more oxygen
then the common form starts
with “per” and ends in “ate”
(ex. NaNO3 = Sodium Nitrate,
NaNO2 = Sodium Nitrite, NaNO =
Sodium Hyponitrite, NaNO4 =
Sodium Pernitrate)
V. Acids: All have H as the first element and
are disolved in water (aqueous or “aq”)
1. Can be named as salts if not
dissolved in water
2. Binary Acids: hydrogen + non-metal
a. named by changing hydrogen to
“hydro”
b. change non-metal ending to “ic”
(change “ide” to “ic”)
c. followed by the word “acid”
(ex: HCl = hydrochloric acid)
3. Ternary acids – hydrogen + radical
a. named for the radical; “ate”
changes to “ic” and is followed
by “acid” (ex: HNO3 = Nitric
Acid)
b. “ite” changes to “ous”
c. also uses “hypo” and “per”
VI. Molecular Compounds: Non-metal plus
non-metal
A. Greek system of naming
1. only used for two non-metals
2. ends in “ide”
3. number of each kind of atom is
indicated by a greek numerical
prefix.
a. mono = 1
b. di = 2
c. tri = 3
d. tetra = 4
e. penta = 5
f. hexa = 6
(ex: CO2 is Carbon Dioxide)
• mono is usually omitted except in
carbon monoxide (CO)
• some names for compounds don’t fit
the rules (ex: H2O = water, NH3 =
ammonia)