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10.2 When Chemicals React
2. How do we know one compound from another?
1.1
Relate an atom’s electron configuration to its Periodic Table row and group.
1.1B *Extension: Investigate the s, p, d and f blocks of the Periodic Table.
1.2 Describe trends in reactivity and metallic character across a row and down a group on the
Periodic Table, and so predict those properties for a given element.
1.3
Define ‘isotope’ and ‘radioisotope’ and give examples.
1.4
Explain that natural radioactivity arises from the decay of
nuclei in atoms, releasing particles and energy.
1.5
Identify examples of the medical and industrial use of nuclear
2.1 Draw models to represent an atom, ion and isotope.
2.2 Construct formulas for a range of ionic compounds, including those containing common polyatomic ions.
2.3 Name ionic compounds from their formulas using -ide, -ite and -ate endings.
2.4 Define salt as a positive metal ion joined to a negative ion (non-metal or polyatomic).
MONDAY P6 L3
MONDAY P6 L3
Chem Flip Note.docxWEDNESDAY P2 L3
WEDNESDAY P2 L3
Writing Formulas for Binary Ionic Compounds
Writing Formulas for Binary Ionic Compounds
Different professions use a type of shorthand in communication to save time. Chemists use chemical symbols in combination to indicate specific compounds. There are two advantages to this approach:
The compound under discussion is clearly described so there can be no confusion about its identity.
Chemical symbols represent a universal language that all chemists can understand, no matter what their native language is.
If you know the name of a binary ionic compound, you can write its chemical formula. Start by writing the metal ion with its charge, followed by the nonmetal ion with its charge. Because the overall compound must be electrically neutral, decide how many of each ion is needed in order for the positive and negative charge to cancel each other out. For aluminum nitride, the ions are:
Al3+
N3−
Since the ions have charges that are equal in magnitude, one of each will be the lowest ratio of ions in the formula. The formula of aluminum nitride is AlN.
The ions for the compound lithium oxide are:
Li+
O2−
In this case, two lithium ions are required to balance out the charge of one oxide ion. The formula of lithium oxide is Li2O.
An alternative way to writing a correct formula for an ionic compound is to use the crisscross method. In this method, the numerical value of each of the ion charges is crossed over to become the subscript of the other ion. Signs of the charges are dropped. Shown below is the crisscross method for aluminum oxide.
The red arrows indicate that the 3 from the 3+ charge will cross over to become the subscript of the O. The 2 from the 2− charge will cross over to become the subscript of the Al. The formula for aluminum oxide is Al2O3.
Be aware that ionic compounds are empirical formulas and so must be written as the lowest ratio of the ions. In the case of aluminum nitride, the crisscross method would yield a formula of Al3N3, which is not correct. It is reduced to AlN. Following the crisscross method to write the formula for lead(IV) oxide would involve the following steps:
The crisscross first yields Pb2O4 for the formula, but that must be reduced to the lower ratio and PbO2 is the correct formula.
TASK 2.2B
TASK 2.2B
View the PPT and complete the practice tasks
10.2 WCR 2.2 Writing Formulas for Ionic Compounds.pptxReview: If you need extra for this outcome
Review: If you need extra for this outcome
View videos:
Writing Formulas for Binary Ionic Compounds https://youtu.be/bPoxAdcYIHU [8.00 mins]
Writing Formulas https://youtu.be/vscoYh6m46M [10.00 mins]
10.2 WCR 1.2 Patterns Periodic Table.docTHURSDAY P4 L3
THURSDAY P4 L3
IRP Check in 1
IRP Check in 1
FRIDAY P2 L3
FRIDAY P2 L3
TASK 2.2C
TASK 2.2C
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