Grade: 11
Course: Chemistry 20
Topic: Covalent bonding
Duration: Two periods
*On second thought, I will probably replace the worksheets with questions from the text-book. I will
have some worksheets ready for Monday though, since I currently do not have the chemistry 20 text”
Day one:
Part 1: Differences between ionic and covalent bonding
- The differences between ionic and covalent bonds will be introduced:
Explain that ionic bonds consist of an “agreement” between an electron donor and an electron
taker. An electron is “exchanged” in an ionic bond. Covalent bonds consist of two or more
elements sharing valence electrons. Neither element is taking or giving an electron; rather, they
are both contributing single valence electrons to form stable pairs. Highlight the above
difference – ionic bonding involves electron giving and taking (the cation is “emptying” an
electron shell while the anion is “filling” one), whereas covalent bonding involves electron
sharing to form stable electron pairs.
Also discuss the fact that ionic bonds form between metals and non-metals whereas as covalent
bonds form between non-metals. The concept of double and triple bonds should be introduced
(ionic bonds are singular; covalent bonds can be singular or multiple – think of CO2)
Illustrate the above explanation on the white board. Have the students follow along with their
chemistry set manipulatives (optional).
Part 2: Linking the Bohr model to ionic and covalent bonding
- Using the white board, link the Bohr model to ionic and covalent bonding:
Complete the Bohr model diagrams for Na and Cl. Next, write the Bohr model diagrams for Na+
and Cl- (these are to be placed directly below the Na and Cl Bohr models – draw an arrow
between them to show the connection). Third, explain what the difference between the two
sets of models is. Finally, connect the Bohr models for Na+ and Cl- in an ionic bond.
Next, repeat the above procedure for CH4. Write out the Bohr diagrams for carbon and
hydrogen. Next, connect the two in the manner of a covalent bond (the shells will overlap). Note
the distinction between ionic and covalent bonds in terms of the placement of electrons both
between the two elements and within the energy shells of each respective atom. The ionic bond
involved the TRANSFER (sort of) of an electron from sodium to chloride, whereas the covalent
bond involved the SHARING of VALENCE electrons (both atoms “gain” an electron, and both
elements are non-metals.
- Write 6 questions on the board. The questions will consist of a list of ions arranged in pairs. The
students will draw the Bohr model for the ions, linking the two models together to form either an ionic
or covalent bond. The students will be given 15 minutes to complete the questions. The questions will
be corrected in class.
Part 3: Covalent bonding nomenclature
- Introduce the Greek prefix naming convention. Highlight the similarities between the naming
conventions for ionic and covalent compounds. Explain that the only true differences are as follows:
Greek prefixes are used when naming covalent molecules. The prefixes are used for both the
first and second elements listed (no prefix for mono in regards to the FIRST element).
Place the left-most element (with regards to the periodic table) first.
The –ide suffix is still applied to the second element listed. The first element does not receive
the suffix despite also being a non-metal.
Both elements comprising the compound are non-metals (found to the right of the staircase on
the periodic table).
Do not reduce the formulae
- Provide as many examples of covalent bond naming as necessary.
- Students will be asked to complete a short worksheet on covalent nomenclature.
Part 4: Covalent formula writing conventions
- Provide several examples of writing the chemical formulae for covalent molecules.
- Explain that the formula writing conventions for covalent molecules are very similar to the conventions
used for ionic bonding.
- Students will be asked to complete a short worksheet on covalent formula writing.
Day two:
Part 5: Review and work session
- Review the concepts introduced during ionic and covalent bonding sessions. Provide numerous
examples.
- Students will be given the remainder of the period to complete a mixed worksheet on covalent and
ionic formula writing and nomenclature.