Chem 142
Name ________________________________________
Summer 2011
Section ________________
Worksheet 2: Atoms, Molecules and Ions
1. A 5.00g sample of magnesium phosphate contains 1.39g of magnesium.
How much magnesium would a 1.00 kg sample contain?
mass fraction =
1.39g Mg
= 0.278 ( Mg sample)
5.00g sample
mass magnesium = 0.278 ( Mg sample ) ! 1.00kg = 0.278kg
2. What mass of sodium is in a 4.6g sample of sodium nitrate?
M NaNO3 = 22.990 + 14.001 + ( 3 ! 15.999 ) = 84.995 g mol
mass fraction =
22.990g Na
= 0.271( Na sample)
84.995g sample
mass sodium = 0.271( Na sample ) ! 4.6g sample = 1.2g Na
3. For each of the following statements, classify the statement as true or
false and explain.
a. Protons, neutrons and electrons all have approximately the same
mass.
False, electrons are 3 orders of magnitude smaller than
protons and neutrons.
b. Atoms with the same number of protons have identical chemical
properties.
True, the type of element is determined by the
number of protons, any atom of the same element will have
identical chemical properties.
c. All neutral atoms of an element have the same number of protons,
neutrons and electrons. False, isotopes are neutral but have a
different number neutrons.
d. A compound cannot be a pure substance.
False, a pure
substance contains only one type of molecule.
e. Both ionic and covalent bonds are formed by the sharing of
electrons. False, an ionic bond is formed between two ions (a
cation and an anion).
f. An ion is formed by the gaining or losing of electrons.
True,
an ion is a charged atom or molecule created by the gaining or
losing of electrons.
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Chem 142
Summer 2011
4. Predict the ion formed by each of the following elements:
a. Sr
Sr2+
b. P
P3c. Rn
Rn
d. Ra
Ra2+
e. Li
Li+
f. O
O25. Determine the chemical formula and name of the ionic compound
formed by each of the following pairs of elements:
a. sodium and oxygen
Na2O
b. aluminum and chlorine AlCl3
c. calcium and fluorine
CaF2
d. strontium and nitrogen Sr3N2
e. rubidium and sulfur
Rb2S
6. Determine either the chemical formula or name of the following ionic
compounds containing Type II cations:
a. CoF2
cobalt (II) flouride
b. tin (IV) oxide dihydrate
SnO2 • 2H2O
c. NiCl2
nickel (II) chloride
d. copper (II) sulfide monohydrate
CuS • H2O
e. lead (IV) nitride
Pb3N4
7. Determine the correct name for each of the following ionic compounds
containing polyatomic ions:
a. MgCO3
magnesium carbonate
b. CrPO4 • 5H2O
chromium (III) phosphate pentahydrate
c. NH4Cl
ammonium chloride
d. KNO2
potassium nitrite
e. Fe2(SO4)3 • 3H2O
iron (III) sulfate
f. RbClO2
rubidium chlorite
g. LiClO4
lithium perchlorate
h. BaSO3
barium sulfite
i. NaHCO3
sodium bicarbonate
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Chem 142
Summer 2011
8. Determine the formulas for each of the following ionic compounds
containing polyatomic ions:
a. cesium sulfate
Cs2SO4
b. lithium nitrite
LiNO2
c. beryllium hypochlorite
Be(ClO)2
d. rubidium chlorate
RbClO3
e. ammonium chlorite
NH4ClO2
f. sodium perchlorate
NaClO4
g. calcium phosphate
Ca3(PO4)2
h. ammonium chloride
NH4Cl
9. Determine the correct name or chemical formula for each of the
following binary covalent compounds:
a. carbon dioxide
CO2
b. PCl3
phosphorus trichloride
c. The compound formed by two P atoms and five O atoms P2O5
d. CF4
carbon tetraflouride
e. boron tribromide
BBr3
f. NF3
nitrogen triflouride
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