Prescriptive Activities: Facet Cluster 1.5: PF#34
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Prescriptive #34:
34 The student believes that a group of atoms with a charge is a molecule, rather than an
ion.
Materials:
 Student handout
Background:
An ion is defined as any atom or group of atoms that has a charge. For an atom or group of
atoms, if there are more electrons than protons it becomes a negatively charged ion. For
example, an oxygen atom that has gained 2 electrons (e-) from some other atom will now
have a negative 2 charge to become O2-. If an atom or group of atoms loses valence electrons
it will become a positively charged ion such as Na+, which contains 11 protons and only 10
electrons after losing its outermost one.
A polyatomic ion is a group of atoms covalently bonded together that has lost electrons
to other atoms (positive charge), or gained extra electrons from other atoms (negative
charge).
One example is the phosphate ion, PO43- which consists of a phosphorous atom covalently
bonded to 4 oxygen atoms, and this group has gained a total of 3 extra electrons from
another atom or group of atoms.
The ammonium polyatomic ion, NH4+, contains a nitrogen atom covalently bonded to 4
hydrogen atoms. This group of atoms has lost one electron to some other atom or group of
atoms and thus has exactly one more proton than electron.
Directions of Activity:
In the table below identify each of the following species as a molecule or an ion by placing
an X in the appropriate column (If you don’t recognize the names you may want to refer to
the Polyatomic Ion Table):
Species
Ion Molecule
Species
NH3
Nitrate
NH4+
Carbon
dioxide
SO42-
Sulfite
SO3
Carbonate
CO32-
Sulfur trioxide
Ion
Molecule
Prescriptive Activities: Facet Cluster 1.5: PF#34
Teacher Page
Common Polyatomic Ions
C2H3O2-
acetate
OH-
hydroxide
NH4+
ammonium
ClO-
hypochlorite
CO32-
carbonate
NO3-
nitrate
ClO3-
chlorate
NO2-
nitrite
ClO2-
chlorite
C2O42-
oxalate
CrO42-
chromate
ClO4-
perchlorate
cyanide
MnO4-
permanganate
Cr2O72-
dichromate
PO43-
phosphate
HCO3-
bicarbonate
SO42-
sulfate
HSO4-
bisulfate
SO32-
sulfite
HSO3-
bisulfate
CN-
Prescriptive Activities: Facet Cluster 1.5: PF#34
Teacher Page
Teacher Notes:
Answer Key
Species
Ion Molecule
NH3
X
Species
Ion
Nitrate
X
NH4+
X
Carbon
dioxide
SO42-
X
Sulfite
X
Carbonate
X
SO3
CO32-
X
X
Sulfur trioxide
Molecule
X
X