Drawing Covalent Bonds

Overview

Students revise how covalent bonds form when non-metal atoms share pairs of electrons. They then use valence-electron information and Lewis dot diagrams to represent covalent molecules, explaining how shared electrons help atoms achieve a stable outer shell.

Learning intentions

Students will:

• revise the meaning of a covalent bond and identify when it forms
• determine the number of valence electrons in common non-metal atoms
• draw Lewis dot diagrams for simple covalent molecules
• explain how shared electron pairs contribute to stability

Success criteria

• I can explain that covalent bonding involves non-metal atoms sharing electrons.
• I can identify valence electrons for common elements.
• I can draw and label single, double and triple covalent bonds.
• I can check whether my diagram gives hydrogen two electrons and most other atoms a full outer shell.

Curriculum links

• Materials — assessing materials through their physical and chemical properties
• Reactions — describing chemical reactions and applying the law of conservation of mass
• Working scientifically — developing questions and hypotheses for scientific investigation
• Working scientifically — selecting and using scientific tools for accurate observations

Lesson structure (60 minutes)

1. 0–5 min · Hook and retrieval. Display the opening question in the covalent bonding hook slide: “Why do two atoms sometimes share electrons instead of transferring them?” Students complete a quick individual retrieval: define an atom, identify a valence electron, and name one difference between a metal and a non-metal. Take brief responses without correcting every misconception yet.

2. 5–15 min · Explicit revision. Use the bonding revision slides to recap that covalent bonds generally form between non-metal atoms, which share electrons to achieve a more stable outer electron arrangement. Model the language “shared pair”, “bonding pair” and “lone pair”. Reinforce that a line represents one shared pair of electrons. Students annotate a simple atom diagram and answer two oral checks: “How many electrons are shared in one covalent bond?” and “Why does hydrogen form only one bond?”

3. 15–25 min · Teacher modelling. Model Lewis diagrams step by step using hydrogen, chlorine and water on the worked-example slides. Demonstrate the sequence: count total valence electrons; choose the central atom where appropriate; place bonding pairs; complete outer shells; check the total electron count. Explicitly show a single bond in H₂ and Cl₂, and lone pairs in H₂O. Students copy the method and use mini-whiteboards to reproduce each example, holding boards up for a rapid check.

4. 25–40 min · Guided worksheet practice. Distribute the covalent bonding practice worksheet. Students work independently for the first three diagrams, then compare with a partner. The worksheet should include H₂, Cl₂, O₂, H₂O, CO₂ and N₂, progressing from single to double and triple bonds. Circulate and ask students to explain each decision rather than simply correcting diagrams. Pause halfway for a class check of O₂, highlighting that a double bond contains two shared pairs.

5. 40–52 min · Apply and explain. Students complete the worksheet’s explanation and error-analysis questions. They identify and correct an incorrectly drawn CO₂ diagram, explain why N₂ requires a triple bond, and describe the difference between a bonding pair and a lone pair. Early finishers compare the total number of valence electrons before and after drawing a molecule and explain how this demonstrates conservation of electrons. Use the challenge and discussion slides to facilitate feedback.

6. 52–60 min · Plenary and exit assessment. Students complete the final question on the exit-question section: draw the Lewis diagram for ammonia, NH₃, and write one sentence explaining how the diagram shows covalent bonding. Invite two students to display different stages of their working, then resolve errors using the checklist: correct atom arrangement, correct total electrons, appropriate shared pairs, complete outer shells, and hydrogen’s two-electron limit.

Resources

• the covalent bonding slide deck
• the covalent bonding practice worksheet
• Mini-whiteboards and pens
• Periodic tables
• Projector or interactive display
• Coloured pens or pencils
• Exercise books
• Optional molecular model pieces or counters

Assessment

• Check retrieval responses and mini-whiteboards to identify misconceptions about valence electrons, sharing and transferring.
• During worksheet practice, use questioning and observation to assess whether students follow the Lewis-diagram sequence and justify single, double and triple bonds.
• Collect or scan the final ammonia diagram and explanation as an exit assessment. Look for accurate electron counting, three N–H shared pairs and one lone pair on nitrogen.

Differentiation

• Support students with a valence-electron reference table, a worked-example checklist and sentence starters: “The atoms share ___ electrons because…” and “The molecule is stable because…”.
• Provide partially completed electron-dot diagrams for students who need reduced writing or drawing demands; allow use of counters before transferring the model to paper.
• Pair students strategically for verbal rehearsal, while ensuring each student completes an individual diagram.
• Extend confident students by asking them to explain why CO₂ is represented with two double bonds and to design a molecule containing a different number of shared pairs. Use clear visual spacing and large-print worksheet diagrams for students requiring accessibility adjustments.