It is expected that students will write and interpret chemical symbols of elements and formulae of ionic compounds.
Students who have fully met the prescribed learning outcome are able to:
Differentiate between elements and compounds
Write chemical symbols for atoms and ions of elements
(drag-and-drop self test)
Differentiate between atoms and ions in terms of structure,
using Bohr models (glossary)
Write chemical formulae for ionic compounds, including those
involving metals with non-metals, multivalent metals, and
polyatomic ions
Name ionic compounds, given the chemical formula
photo: Salar de Uyuni, Bolivia by turbo@ morguefile
RESOURCES:
Searchable database includes: easy access to chemical synonyms, molecular weights, structures, equilibrium constants, thermodynamic properties, and common uses, with properties presented in a variety of common units. Structure information includes flat structural formulas, ball and stick models, electron density/electric potential maps, and Chime "live" structures that can be rotated and queried for bond lengths, bond angles, and torsion angle
Ionic Compound Construction Kit
Build an ionic compound formula, using elemental or polyatomic ions. You'll use an ion balance to find an electrically neutral combination of ions. The formula for the compound is written step by step from the formulas for the ions.
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PLANNING FOR ASSESSMENT /ASSESSMENT STRATEGIES
With students working in pairs, provide a
card with an element or a compound name
and formula on it. Ask the pair to decide if
it is an element or a compound AND if it is
an atom or a molecule. Tell students you
will ask them to justify their answers.
• After students have categorized their
substances, list them on the O/H or board.
Discuss their choices. Provide a definition of
element and compound, and see if they want
to change any choices.
Ask students to compare the terms element and
compound AND atom and molecule in their
notebooks.
• Provide students with exemplary comparisons
and examples so they can self-evaluate and
correct their work.
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Brainstorm with students reasons that
elements come together to form compounds
(positive ions attract negative ions). Provide
students with a Periodic Table that shows
the ion charges on the elements (slides) and a Table
of Common Ions. Then have students
practise recognizing and writing atom and
ion symbols. They should realize electrons
are lost or gained.
Have students complete an assessment activity
such as the Ion Charge Chart provided at the
end of the Classroom Model for this grade.
Assess the extent to which students are able to
accurately complete the chart.
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Have students draw Bohr diagrams of ions
(1 to 20): negative ions gain electrons to fill
their outermost shell and positive ions lose
electrons.
Collect students’ Bohr drawings, looking for
evidence that they are able to
• correctly identify the number of protons and
electrons in an ion
• predict the ion charge for an element based on
their diagram
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Explain that ionic compounds form when a
metal ion combines with a non-metal ion.
When the two elements chemically
combine, the ion charges are balanced.
Practice with several examples. Models can
be used to visually represent this
relationship.
• Have students practise writing chemical
formulae for ionic compounds:
- Monovalent metal with a non-metal
- Multivalent metal with a non-metal
- Either a monovalent or multivalent
metal with a polyatomic ion
Assign groups of students ten different
elements that form positive ions (or
ammonium) and 10 different elements that form
negative ions (or negative polyatomic ions).
Have students predict possible combinations of
positive and negative ions from these. Have
students check on a web periodic table to see if
their combinations actually exist and if there is
a use for each of their ten compounds.
• Provide students with file cards (approx 30) and
have the groups produce ‘cards’ for 10 different
ion combinations, for example:
- one Na+ card and one Cl- card is one
combination (2 file cards)
- one Al3+ card and three Br- cards is another
combination (4 file cards)
• Ask student groups to demonstrate their ‘card’
arrangements to other student groups. The
cards and arrangements can be evaluated for
- the correct number of ion cards for each
compound
- their attractiveness
- the example provided
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Have students examine a chemical name
(e.g., sodium chloride). Ask the following
questions:
- What happens to the first element’s
name?
- What happens to the second element’s
name?
Guide them to this general ‘rule’:
monovalent metal with a non-metal: the
name of the metal does NOT change and
the non-metal ending is changed to “ide.”
Repeat this strategy with two more
examples to reach the rules for
multivalent metal with a non-metal: The
name of the multi-valent metal is followed
by a Roman Numeral indicating the ion
charge and the non-metal ending changes to
“ide” (e.g., Iron (III) chloride)
either a monovalent or multivalent metal
with a polyatomic ion: The metal is
handled as above and the non-metal
polyatomic ion name is unchanged.
Have students correctly name their
combinations (or the combinations of other
students) from the preceding activity.
