Explain why silicon (Si) is classified as a metalloid rather than as a metal or a non-metal, referring to its position in the periodic table and its physical and chemical properties.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Silicon lies on the zig‑zag boundary between metals and non‑metals in the periodic table (period 3, group 14), a region that contains the metalloids.
It shows a metallic physical property: it is solid at room temperature and has a lustrous, shiny appearance.
It also shows a non‑metallic physical property: it is brittle and not malleable or ductile, and it behaves as a semiconductor rather than a good conductor of electricity.
Because silicon displays both metallic and non‑metallic characteristics, it does not fit neatly into either group and is therefore classified as a metalloid.
It shows a metallic physical property: it is solid at room temperature and has a lustrous, shiny appearance.
It also shows a non‑metallic physical property: it is brittle and not malleable or ductile, and it behaves as a semiconductor rather than a good conductor of electricity.
Because silicon displays both metallic and non‑metallic characteristics, it does not fit neatly into either group and is therefore classified as a metalloid.
Examiner tips
- Mention the staircase position first; link to the zig‑zag boundary. Include at least one metallic and one non‑metallic property. Use the word "metalloid" explicitly. Keep the answer concise to fit the 4 marks.
Common mistakes
- Saying silicon is a metal because it is solid or a non‑metal because it is brittle, without showing both types of properties. Using vague terms like "somewhat" instead of specific properties. Forgetting to mention its position on the staircase or the semiconductor behaviour.
Mark scheme (4 marks)
- Silicon is located on the 'staircase' / zigzag boundary between metals and non-metals in the periodic table (period 3, group 14), a region associated with metalloids.
- Silicon has a physical property characteristic of metals: it has a lustrous / shiny appearance, OR it has a high melting point / is solid at room temperature.
- Silicon has a physical property characteristic of non-metals: it is brittle / not malleable or ductile, OR it is a semiconductor rather than a good conductor of electricity.
- Because silicon exhibits properties intermediate between metals and non-metals (both metallic and non-metallic character), it does not fit neatly into either category and is therefore classified as a metalloid.
Key terms in this question
Related
- All IB DP Chemistry Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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