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CHEMISTRY Naming Compounds Handout page 1
ANSWER KEY
IONIC COMPOUNDS versus MOLECULAR COMPOUNDS
Ionic compound: consist of cations (positive ions) and anions (negative ions)
held together by electrostatic attraction
– usually metal + nonmetal(s)
o - rather large difference in electronegativity of the bonding
elements
– made of monatomic ions, polyatomic ions, and/or both
– monatomic ions: consist of a single atom {e.g. Na+ or F-}
- polyatomic ions: consist of more than one atom {e.g. OH-, NH4+ }
Molecular compound: consist of nonmetal atoms bonded together by
shared pairs electrons (covalent bonding)
– acid: a molecular compound that releases hydrogen ions (H+) when
dissolved in water {often appears as hydronium ion; H3O+(aq)}
NAMING MONATOMIC CATIONS:
Metal atoms tend to lose valence electrons to form positively charged ions, called
cations.
An positive ion formed from an individual atom is a monatomic cation.
-
Groups IA, IIA, IIIA (B+3, Al+3, Ga+3) zinc (Zn+2), cadmium (Cd+2), and
silver (Ag+), form only one type of ion (have one oxidation number):
– Group IA elements form +1 ions: H+, Li+, Na+, K+, Rb+, Cs+
– Group IIA elements form +2 ions: Be+2, Mg+2, Ca+2, Sr+2, Ba2+
- Group IIIA elements forming +3 ions: B+3, Al+3, Ga+3
- Transition elements forming only one positive ion: Ag+, Zn2+, Cd+2
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When a Group IA, IIA, IIIA (first three elements), cadmium, zinc, or silver forms
an ion, it is named:
element name + ion/cation
e.g. Na+ = sodium ion
Sr+2 = strontium cation
Zn+2 = zinc ion
The Stock system or traditional system is used to name transition metals, post
transition metals, and other metals that form more than one positive ion (have
multiple oxidation numbers):
e.g. Iron forms Fe+2 and Fe+3
Lead forms Pb2+ and Pb4+
When a metal can form more than one ion, each ion is named in the Stock System
by:
Element name (charge in Roman numerals) & ion/cation
Fe+2 is the iron (II) ion and Fe+3 is the iron (III) cation
Pb2+ is lead (II) ion and Pb4+ is the lead (IV) cation
Some of the metallic ions are named in the Traditional System using the root of
their name of origin or anglicized name with an –ous or –ic suffix attached. The
–ous suffix is used with the ion of lesser positive charge and the –ic suffix is used
with the ion of greater positive charge.
The name of origin for iron is ferrum and that of lead is plumbum.
Fe+2 is the ferrous cation and Fe+3 is the ferric ion
Pb2+ is the plumbous cation and Pb4+ is the plumbic ion
Other elements of which to be aware are: copper – cuprum, tin – stannum, and
mercury which is hydragyrum BUT IT FORMS a MERCUROUS and a MERCURIC
ION
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**Look up the above elements to determine the cations that they form! Also,
look up the cobaltous/cobaltic ions and the chromous/chromic ions
Name each of the following monatomic cations:
Li+ -
lithium ion
Ag+ - silver ion
Ba+2 – barium cation
Cu+2 (both names) – copper(II)
ion/cupric cation
Al3+ - aluminum cation
Mg++ - magnesium ion
Mn+2 - manganese(II) cation
Mn+7 – manganese(VII) ion
Mn+5 - manganese(V) ion
Mn+4 - manganese(IV) cation
Sn4+ (both names) – tin(IV) ion/stannic cation
Sn+2 (both names)- tin(II) ion/
Stannous cation
Co++- cobalt(II) ion/cobaltous ion
Co+++- cobalt(III) ion/cobaltic cation
Na+1- sodium cation
K1+ - potassium cation
Ni+2 - nickel ion
Ca+2 – calcium ion
Ti+4 - titanium(IV) cation
Cd+2 - cadmium cation
NAMING MONATOMIC ANIONS:
Nonmetal atoms tend to gain valence electrons to form negatively charged ions
called anions.
When a nonmetal forms an ion, it is named:
Element root name - “ide” & ion/anion
e.g. O = oxygen atom which forms the O–2 = oxide ion/anion
N = nitrogen atom which forms the N–3 = nitride ion/anion
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Name each of the following monatomic anions:
F- - fluoride ion
Cl- - chloride ion
S2- - sulfide anion
P-3 – phosphide anion
I- - Iodide anion
Te - - - telluride ion
As3- - arsenide anion
Se-2 – selenide ion
Br- - bromide anion
C4 - - carbide ion
NAMING POLYATOMIC IONS:
Ions made up of more than one atom (covalently bonded) are polyatomic ions.
These ions function as a single unit:
– only one polyatomic cation: NH4+ = ammonium ion
-
Also be aware of the mercurous ion which is a diatomic ion; Hg22+
– there are many polyatomic anions: see table below:
Polyatomic cations
NH4+ is the ammonium ion
Polyatomic anions – most of these are oxyanions (negatively charged and
contain oxygen bonded to a central atom) – many of these ions end in –ate or
-ite
NO2- = nitrite ion
NO3- = nitrate ion
MnO41 - = permanganate ion
ClO3-1 = chlorate
HCO3-1 = hydrogen carbonate or bicarbonate ion
ClO4- = perchlorate
ClO2-1 = chlorite
ClO- = hypochlorite
HSO4- = hydrogen sulfate or bisulfate
C2H3O2- = acetate ion
BrO3- = bromate
IO3- = iodate
SCN- = thiocyanate
HSO3- = bisulfite or hydrogen sulfite
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Some are nonoxyanions; these end in “–ide”
OH– = hydroxide ion
CN- = cyanide ion
N3- = azide
NH2- = amide
O2-2 = peroxide ion
Negative two
CrO4-2 = chromate ion
SO4-2 = sulfate ion
CO3-2 = carbonate ion
Cr2O7-2 = dichromate ion SO3-2 = sulfite ion
SeO4-2 = selenate ion
TeO4-2 = tellurate ion
SiO3-2 = silicate ion
C2O4-2 = oxalate ion
S2O3-2 = thiosulfate ion
Negative three
PO4- 3 = phosphate ion
AsO4 -3 = arsenate ion
BO3-3 = borate
Some of the oxyanions follow a system of naming:
Oxyanion – a negatively charged oxygen bearing ion
The most common ion is often from the “– ate” group of ions – memorize
these ions!!
If the ion’s central atom increases in charge or an oxygen is added compared
to the _ate form, retain the charge and the name of the ion will be:
per-__________-ate
If the ion’s central atom decreases in charge or an oxygen is lost from the –
ate form of the ion, the name of the ion becomes:
_________ - ite
If the ion’s central atom decreases in charge or an oxygen is lost from the –
ite form the ion becomes:
hypo - __________ - ite
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Example
Name
Formula
Charge on central atom
perchlorate
ClO4 -
Cl
chlorate
ClO3 -
Cl +5
chlorite
ClO 2
-
Cl +3
hypochlorite
ClO -
Cl
+7
+1
Name each of the following polyatomic ions:
ClO- = hypochlorite ion
Cr2O7-2 = dichromate ion
OH- = hydroxide ion
CO3-2 = carbonate ion
PO4-3 = phosphate ion
BO3-3 = borate ion
SeO4-2 = selenate ion
NO3- = nitrate ion
HSO3- = bisulfite/hydrogen sulfite ion
CN- = cyanide ion
CrO4-2 = chromate ion
O2-2 = peroxide ion
WRITING CHEMICAL FORMULAS GIVEN INDIVIDUAL IONS
**All compounds must be electrically neutral (electroneutrality).
Therefore, the total positive charge in the compound {# positive ions x the
charge on each ion} must equal the total negative charge (# of negative ions x
the charge on each ion} in the compound.**
Subscripts are manipulated to obtain the simplest ratio of ions that will
produce a neutral chemical formula!
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1. If the two ions have exactly the same, but opposite charges (+1 and –1, +2 and –2,
+3 and –3) then by “simple inspection” there must be one of each ion present in the
formula. Combines in a 1 to 1 ratio.
e.g. Na+ & I- combine to form NaI
Mg+2 & O-2 combine to form MgO
Al+3 & N-3 combine to form AlN
2. If two monatomic ions have different charges;
Identify the charge on each of the combining ions.
a. Use trial and error
e.g. Ca+2 & F- Start with 1 to 1 ratio
CaF
one (+2) and 1 (- 1) = + 1 net charge
therefore, not correct – excessive positive charge
so increase the number of negative ions
CaF2
one (+ 2) and 2 (- 1) = 0 for net charge
therefore, correct formula!
b. Use the least common multiple of the absolute values of the charges
on the ions
e.g. combining potassium (K+) and phosphate (PO4-3)
The LCM of │+1│ and │-3│ is 3
To obtain the subscripts of the ions, divide the LCM by the absolute
value of the charge on that ion and use the result as a subscript
For potassium’s subscript: 3 / │1 │= 3
For phosphate’s subscript: 3 / │- 3│ = 1
The formula will be K3PO4
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c.Use crossover rule (criss-cross) to get formula of the compound
– the absolute value of the superscript for cation becomes subscript
for anion
- the absolute value of the superscript for anion becomes subscript
for cation
(Note: Only the numbers cross down, not the signs!)
Beware - simplify subscripts to get simplest ratio of ions,
excepting mercury(I)
Ionic compounds are usually represented by empirical
formulas
e.g combining nickel(II) and iodine
Ni+2 and IUse the 2 for the subscript of iodine and the 1 for the subscript of nickel to
get NiI2
Ni+2
I-1
Recall, a subscript of one (1) is NEVER EXPRESSED – it is redundant!!
e.g combining magnesium (Mg+2) and carbonate (CO3-2)
Use the two for the subscript of magnesium and the two for the subscript
of carbonate to produce Mg2(CO3)2. HOWEVER, these subscripts need to be
reduced to form MgCO3.
Recall: if only one polyatomic ion is present in the formula, no parentheses are
used. But, if two or more polyatomic ions are present, the formula of the ion is
placed inside parentheses and the subscript is placed outside!!
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Naming Compounds
In order to correctly name a compound, the appropriate nomenclature system must
be utilized. Therefore, the first step is identifying the compound; is it organic,
ionic, molecular, an acid, or a hydrate.
Ionic compounds – metal – nonmetal; metal – polyatomic anion; or polyatomic
cation – polyatomic anion; polyatomic cation - nonmetal
Molecular compounds – nonmetal – nonmetal; hydrogen - polyatomic ion;
hydrogen – nonmetal
Acids – solubilized hydrogen – nonmetal; solubilized hydrogen – polyatomic
ion
Solubilized – meaning dissolved in water, and therefore, usually
represented with an (aq) phase symbol
Hydrates – ionic salts with water molecules weakly attached
Organic – carbon based in which C is covalently bonded, mainly with hydrogen
(H). However, organic compounds may at times contain some nitrogen (N),
sulfur (S), phosphorus (P), oxygen (O).
NOTE EXCEPTIONS are CO, CO2, and CO32Ionic compounds –
Name the positive ion (cation) first
If a polyatomic ion, merely write its name
If a metal from Groups I A or II A, IIIA (B, Al, Ga), or Zn, Cd, Ag;
merely write the metal’s name
Any other metal, determine the charge on the metallic ion and use
either its traditional name (-ic/ous) or the Stock name (Roman
numeral in parentheses)
To determine the charge on the metal ion:
1) Determine total negative charge in the formula
(compound).
2) Change the negative sign to a positive sign as all
compounds are neutral, therefore total negative charge
MUST EQUAL total positive charge
3) Divide the total positive charge by the number of
metallic ions to get the charge per cation
Note – in all cases, the term ion is omitted!!
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Name the negative ion last
If a nonmetal, modify its name for the –ide suffix
If a polyatomic ion, merely write its name
e.g. MgCl2 – magnesium chloride
e.g. FeSO3 – iron (II) sulfite or ferrous sulfite
e.g. (NH4)2CO3 – ammonium carbonate
Molecular compounds –
Binary compounds composed of two nonmetals.
Traditional naming uses prefixes to indicate the number of atoms of each
element present in a molecule of the compound
Mono-; di-; tri-; tetra-; penta-; hexa-; hepta-; octa-; nona-; decaNOTES - The mono- is dropped on the more positive element and the
vowel of a two syllable prefix is dropped if the nonmetal name begins
with a vowel
Stock naming is similar to that used for ionic compounds
The more positive element is named first followed by the more negative
element modified for the –ide suffix
e.g. N2O5 – dinitrogen pentoxide or nitrogen (V) oxide
e.g. PCl3 – phosphorus trichloride or phosphorus (III) chloride
NOTE: use the traditional or use the Stock, but do not combine the
two!
Organic
Organic compounds have their own unique nomenclature system based upon
the type of organic compound.
Alkanes – CnH2n+2 ; Alkenes - CnH2n ; Alkynes - CnH2n-2 ; alcohols which
contain an OH (hydroxyl group)
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Prefixes based upon the number of carbon atoms in a chain: meth-, eth,prop-, but-, pent-, hex-, hept-, oct-, non-, decAlkanes attach a, “-ane” suffix or ending to the prefix
Alkenes attach an “-ene” suffix or ending to the prefix
Alkynes attach an “-yne” suffix or ending to the prefix
Alcohols attach an “-anol” to the prefix
In addition, numbers are used to indicate position of the double bond, triple
bond, or –OH group in an alcohol.
e.g.
2-pentene
Acids – the are often solubilized (dissolved in water) molecular compounds
e.g. HCl(aq), HNO3(aq), H2SO4(aq)
Naming acids
Binary acids are composed of hydrogen and a nonmetallic element
They are named using the form:
hydro – nonmetal root – ic
This form is also used by any non-oxyacid as well
e.g. HCl(aq) – hydrochloric acid
H2S(aq) – hydrosulfuric acid
HI(aq) – hydroiodic acid
Oxyacids contain hydrogen and an oxyanion (negative polyatomic ion w/
oxygen bonded to a central atom (often a nonmetal))
They are named using the form:
anion prefix – anion root – ic/-ous
(if present)
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The –ate ions become –ic acids and the –ite ions become –ous acids
e.g. HNO3 – nitric acid
HNO2 – nitrous acid
H2SO4 – sulfuric acid
H2SO3 – sulfurous acid
HClO4 – perchloric acid
HClO – hypochlorous acid
Hydrates – these are ionic salts that have water molecules weakly attached to
them in a specific ratio
These “waters of hydration” are usually driven off by heating the hydrate
which leaves the anhydrous residue (ionic salt)
Note the form of a hydrated compound’s formula
Anhydrous salt formula • coefficient water’s formula
e.g. MgSO4 • 7 H2O
CuSO4 • 5 H2O
Naming these hydrates involves writing the name of the anhydrous salt first
followed by a prefix attached to the word hydrate. The Greek prefix refers to the
coefficient before the formula of water. The word hydrate refers to water.
The names of the compounds above would respectively be:
magnesium sulfate heptahydrate
copper (II) sulfate pentahydrate or cupric sulfate pentahydrate
What would be the anhydrous salt that remains after heating the above hydrates?
magnesium sulfate
and copper(II) sulfate or cupric sulfate
How is a hydrate different from other chemical compounds?
Hydrates contain water molecules present in the structure in a
defined ratio per formula unit of salt
Define the following terms:
Anhydrous – without water/containing no water
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Dehydration – to remove water
Name the following compounds:
a)
FeCl3 • 6 H2O _ferric chloride hexahydrate/iron(III) chloride
hexahydrate
b)
BaCl2 • 2 H2O barium chloride dihydrate
Write the formulas for the following compounds:
a)
sodium carbonate decahydrate _Na2CO3 • 10 H2O__
b)
strontium chloride hexahydrate _SrCl2 • 6 H2O___
Name the following compounds
1)
Na2CO3 _sodium carbonate________
2)
NaOH _sodium hydroxide__________
3)
HBr _hydrogen bromide _______
4)
MgBr2 _magnesium bromide__________
5)
KCl _potassium chloride_____________
6)
N2S3 _dinitrogen trisulfide/nitrogen(III) sulfide_______
7)
FeCl2 _iron(II) chloride/ferrous chloride_________
8)
FeCl3 _iron(III) chloride/ferric chloride______
9)
SiF4 _silicon tetrafluoride/silicon(IV) fluoride_____
10)
Zn(OH)2 _zinc hydroxide___________________________
11)
BeSO4 _beryllium sulfate____________________________
12)
SO3 _sulfur trioxide/sulfur(VI) oxide___________
13)
HClO3(aq) _chloric acid____________
14)
N2O3 _dinitrogen trioxide/nitrogen(III) oxide_____________
CHEMISTRY Naming Compounds Handout
15)
Al2S3 _aluminum sulfide_____________________________
16)
PbO _plumbous oxide/lead(II) oxide_________
17)
HBr(aq) _hydrobromic acid_______
18)
Li3PO4 _lithium phosphate________
19)
TiI4 _titanium(IV) iodide________
20)
Co3N2 _cobalt(II) nitride/cobaltous nitride__________
21)
Mg3P2 __magnesium phosphide______________
22)
Ga(NO2)3 _gallium nitrite________________
23)
Ag2SO3 _silver sulfite____________
24)
H2S(aq) _hydrosulfuric acid____________
25)
NH4OH ammonium hydroxide________
26)
Al(CN)3 _aluminum nitrate_____________
27)
Be(CH3COO)2 _beryllium acetate_________
28)
NO _nitrogen monoxide/nitrogen(II) oxide________
29)
P4O10 _tetraphosphorus decoxide__________
30)
H2SO4(aq) _sulfuric acid____________
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Write chemical formulas for the following compounds
1)
copper (II) chloride _CuCl2________________________
2)
lithium acetate _LiC2H3O2____________________________
3)
nitrous acid _HNO2(aq) _______________________________
4)
vanadium (III) selenide _V2Se3______________________
5)
sulfur hexachloride _SCl6_________________________
6)
manganese (IV) nitride _Mn3N7______________________
7)
beryllium oxide _BeO____________________________
CHEMISTRY Naming Compounds Handout
8)
chlorous acid __HClO2(aq)_____________________________
9)
sulfur dioxide _SO2______________________________
10)
sodium sulfate _Na2SO4_____________________________
11)
aluminum arsenide _AlAs__________________________
12)
diboron hexahydride _B2H6________________________
13)
potassium permanganate _KMnO4______________________
14)
chromium (VI) cyanide __Cr(CN)6______________________
15)
hydrobromic acid __HBr(aq)____________
16)
tin (II) sulfite _SnSO3_______________
17)
vanadium (V) fluoride _VF5____________
18)
nitrogen tribromide _NBr3_____________
19)
ammonium nitrate _NH4NO3____________
20)
diphosphorus pentoxide _P2O5___________
Write the names of the following compounds
1)
NaBr _sodium bromide__________
2)
Ca(C2H3O2)2 _calcium acetate__________
3)
P2O5 _diphosphorus pentoxide_________
4)
Ti(SO4)2 __titanium(IV) sulfate___________
5)
FePO4 __iron(III) phosphate/ferric phosphate_____
6)
K3N _potassium nitride________
7)
SO2 _sulfur dioxide/sulfur(IV) oxide_________
8)
CuOH _copper(I) hydroxide/cuprous hydroxide____
9)
Zn(NO2)2 _zinc nitrite_________________
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CHEMISTRY Naming Compounds Handout
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10)
V2S3 _vanadium(III) sulfide_________________
11)
CoCl2 • 2 H2O _cobalt(II) chloride dehydrate or cobaltous chloride
dihydrate_
12)
NiSO3 • 6 H2O _nickel(II) sulfite hexahydrate _____
Write chemical formulas for the following compounds.
13)
silicon dioxide _SiO2_______________________
14)
nickel (III) sulfide _Ni2S3___________________
15)
manganese (II) phosphate _Mn3(PO4)2______
16)
silver acetate _AgC2H3O2___________
17)
diboron tetrabromide _B2Br4_________
18)
cupric chloride dihydrate _CuCl2 • 2 H2O______
19)
potassium carbonate _K2CO3__________
20)
ammonium chlorate _NH4ClO3__________
21)
tin (IV) selenide _SnSe2______________
22)
carbon tetrachloride _CCl4___________________
23) barium iodide dihydrate _BaI2 • 2 H2O_______