Year 9 Science · Unit 2 · Lesson 10
Challenge Worksheet
Learning Goals
Find the mistake
A student wrote this answer
"All three types of bonding, ionic, covalent, and metallic, are basically the same: they all involve electrons being shared between atoms. The difference is just how many electrons are shared. Ionic bonds share 1 electron, covalent bonds share 2, and metallic bonds share all the electrons. This is why metallic bonds are the strongest."
1. Identify at least three scientific errors or misleading statements in the student's answer. List each one clearly.
2. Write a corrected version of the student's answer. Use the correct scientific language for each bond type. Your version should clearly explain what happens to electrons in each type of bonding.
3. Explain why using the word "sharing" to describe ionic bonding is particularly misleading. What actually happens to the electron in ionic bonding?
1. Steel is an alloy of iron and carbon. Iron has metallic bonding; a small amount of carbon atoms (about 0.2–2.1%) is added into the iron lattice. Pure iron is soft and bends easily; steel is much harder and stronger. Using metallic bonding theory, explain why adding a small amount of carbon to iron produces a material that is significantly harder and stronger than pure iron.
2. Tungsten (W) is a metal with a melting point of 3422 °C, the highest of any pure metal. Some ionic ceramics (e.g. magnesia, MgO) melt at 2852 °C. A student claims: "Ionic compounds always have higher melting points than metals because ionic bonds are stronger." Evaluate this claim. In your answer, use evidence from these two substances and explain what actually determines melting point in each bond type.
Wrap Up
In one sentence, what was the main idea of this lesson?