Naming Molecular (Covalent) Compounds
We also need to take up the matter of naming covalent compounds. Covalent compounds are
named in different ways than are ionic compounds (although there is some overlap). Many of these
compounds have common names such as "methane", "ammonia" and "water". However, simple
covalent compounds are generally named by using prefixes to indicate how many atoms of each
element are shown in the formula. Also, the ending of the last (most negative) element is changed
to -ide.
The prefixes used are mono-, di-, tri-, tetra-,
penta-, hexa-, and so forth. The mono- prefix is
usually not used for the first element in the
formula. The "o" and "a" endings of these prefixes
are dropped when they are attached to "oxide."
1
mono-
2
di-
3
tri-
4
tetra-
5
penta-
6
hexa-
You also need to know which element to put first
in the formulas and names of these compounds.
Generally, they are in the same left-to-right
order that they have on the periodic table,
except that you would have to squeeze hydrogen
in between nitrogen and oxygen.
At this time, try the following practice problems (also found in exercise 12 in the workbook).
Name the following compounds.
PH3
CO
HI
N2O3
SCl6
P2O5
SO3 (notice: no charge)
NH3
Naming Ionic Compounds
Name the cation (Determine the charge of the transition metal if more than one
option is available- AND use that in the name) and then name the anion.
Give the name of the following ionic compounds:
1) Na2CO3 ____________________________________________________
2) NaOH _____________________________________________________
3) MgBr2 _____________________________________________________
4) KCl _______________________________________________________
5) FeCl2 ______________________________________________________
6) FeCl3 ______________________________________________________
7) Zn(OH)2 ___________________________________________________
8) BeSO4 ___________________________________________________
9) CrF2 ______________________________________________________
10) Al2S3 _____________________________________________________
11) PbO ______________________________________________________
12) Li3PO4 ____________________________________________________
13) TiI4 _______________________________________________________
14) Co3N2 ____________________________________________________
15) Mg3P2 ____________________________________________________
16) Ga(NO2)3 __________________________________________________
17) Ag2SO3 ____________________________________________________
18) NH4OH ____________________________________________________
19) Al(CN)3 ____________________________________________________
20) Be(C2H3O2)2 ______________________________________________
Writing Ionic Formulas
For the following compounds, give the formulas
22) sodium phosphide ___________________________________________
23) magnesium nitrate ___________________________________________
24) lead (II) sulfite ______________________________________________
25) calcium phosphate ___________________________________________
26) ammonium sulfate ___________________________________________
27) silver cyanide _______________________________________________
28) aluminum sulfide ____________________________________________
29) beryllium chloride ____________________________________________
30) copper (I) arsenide ___________________________________________
31) iron (III) oxide _______________________________________________
32) gallium nitride _______________________________________________
33) iron (II) bromide _____________________________________________
34) vanadium (V) phosphate ______________________________________
35) calcium oxide _______________________________________________
36) magnesium acetate __________________________________________
37) aluminum sulfate ____________________________________________
38) copper (I) carbonate __________________________________________
39) barium oxide ________________________________________________
40) ammonium sulfite ____________________________________________
41) silver bromide _______________________________________________
42) lead (IV) nitrite ______________________________________________
Rules for Naming Simple Acids and Oxyacids
How do you recognize that something is an acid? The acids that we will be concerned with naming are really
just a special class of ionic compounds where the cation is always H+. By convention, cations are written first in
ionic formulas. So if the formula has hydrogen written first, then this usually indicates that the hydrogen is an
H+ cation and that the compound is an acid. When dissolved in water, acids produce H+ ions (also called
protons, since removing the single electron from a neutral hydrogen atom leaves behind one proton). If the
counterion (the anion) to H+ in the acid is a polyatomic ion that contains oxygen (like NO2- or PO43-), the acid is
called an oxyacid and is named using the rules provided below. If the anion does not contain oxygen, as in the
case of F- or the polyatomic ion CN-, then a different set of rules are used for naming the acid.
Rules for Naming Oxyacids (anion contains the element oxygen):





Since all these acids have the same cation, H+, we don't need to name the cation.
The acid name comes from the root name of the oxyanion name or the central element of the oxyanion.
Suffixes are used based on the ending of the original name of the oxyanion. If the name of the polyatomic
anion ended with -ate, change it to -ic for the acid and if it ended with -ite, change it to -ous in the acid.
-ate becomes –ic
and
-ite becomes -ous
So, HNO3, which contains the polyatomic ion nitrate, is called nitric acid. The acid HNO2, which contains the polyatomic
ion nitrite, is called nitrous acid.
Rules for Naming Acids that Do Not Contain Oxygen in the Anion:





Since all these acids have the same cation, H+, we don't need to name the cation.
The acid name comes from the root name of the anion name.
The prefix hydro- and the suffix -ic are then added to the root name of the anion. So, HCl, which contains the
anion chloride, is called hydrochloric acid. HCN, which contains the polyatomic ion cyanide, is called hydrocyanic
acid.
Name the following acids
1. HCl
2. HClO4
3. HIO3
4. HI
5. H2SO4
6. H2S
7. HCN
8. H2CO3
9. HBrO4
10. HBrO3
11. HC2H3O2
12. H3PO3
14. H2CrO4
15. H2Cr2O7
Give formulas for the following acids
17. hydrofluoric acid
18. nitric acid
19. nitrous acid
21. periodic acid
22. carbonic acid
23. hypobromous acid
24. bromous acid
25. permanganic acid
27. iodous acid
28. sulfurous acid
29. sulfuric acid
30. perchloric acid
31. chlorous acid
32. acetic acid
33. phosphoric acid
34. phosphorous acid
Molecular Mass and Percent Composition Worksheet
Find the molecular mass of each of the following to two decimal places AND use appropriate
units.
ex: H20: 2(1.01) + 1(16.00) = 18.02 grams/mole (**note the unit)
1. CO
2. CO2
3. CeBr3
4. H2SO4
5. CuSO4
6. H2CO3
7. MgSO4
8. C6H12O6
9. C2H3O
10. C2H5OH
Determine the percent composition of each element in the following compounds. Express
answers to two
decimal places.
ex: SO2 SO2 = 32.07 + 32.00 = 64.07
% S = mass S/mass SO2 X 100; 32.066/64.064 X 100 = 50.053% = 50.05%
% O = mass O/mass SO2 X 100; 31.998/64.064 X 100 = 49.946 % = 49.95%
11. CO2
12. CH2O
13. H2SO4
14. CuSO4
15. CHCl3
16. C12H22O11
17. C14H20N2SO4
The Mole Is What Brings it Together
1 mole = 6.02 x 1023 molecules = 22.4 L (@ STP)
1.
Calculate the mass of 1.58 moles CH4. [molar mass CH4 = 16.0 g/mol]
1.58 moles CH4
2.
What volume will 7.29 moles of CO2 gas occupy at STP?
7.29 moles CO2
3.
=
=
How many molecules are there in a 0.00583 mole sample of H2O?
0.00583 moles H2O
=
4.
What mass of CO2 gas occupies a volume of 100. Liters at STP? [molar mass CO2 = 44.0 g/mol]
5.
How many molecules are in a 35.0 gram sample of H2O? [molar mass H2O = 18.0 g/mol]
6.
What volume will 5.25 x 1022 molecules of CH4 occupy at STP?
7.
What volume will 2.22 moles of CO2 gas occupy at STP?
8.
How many molecules are there in a 0.127 mole sample of H2O?
9.
What mass of CO2 gas occupies a volume of 395 Liters at STP? [molar mass CO2 = 44.0 g/mol]
10. Given 28.08 grams of C4H10
a. How many moles of butane molecules are present?
b. How many water molecules are present?
c. How many moles of C atoms are present? How many C atoms?
d. How many moles of H atoms are present? How many H atoms?