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ICSE Class 7 Chemistry Question 11 of 16

Metals and Non-metals — Question 10

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Question 10

State what are metalloids. Name the elements recognized as metalloids. Compare the properties of metalloids with those of metals. State the uses of three different metalloids.

Answer

Metalloids are elements that show the properties of both metals and non-metals. They have physical and chemical properties, intermediate between those of metals and non-metals.

Elements like Boron [B], Silicon [Si], Germanium [Ge], Arsenic [As], Antimony [Sb], Tellurium [Te] are recognized as metalloids.

Comparison of properties:

PropertyMetalMetalloids
StateSolids at room temperatureSolids at room temperature
NatureGenerally, hard in nature.Brittle in nature.
ConductivityGood conductors of heat and electricity.Semi conductors of electricity and show average transmission of heat.
LustreShow brightnessShow brightness
Malleability & DuctilityMalleable and DuctileGenerally malleable and Ductile

Use of metalloids:

  1. Boron — is used as an insecticide and a fire retardant.
  2. Arsenic — is used for certain medicinal purposes.
  3. Silicon — Silicon gel is generally applied to burn patients and to absorb moisture.

ICSE Class VII Chemistry Chapter 5 14 Marks

Metals and Non-Metals — Quick Study Guide

Elements are broadly classified as metals, non-metals, or metalloids based on their physical and chemical properties.

Key Properties

  • Metals: Lustrous, malleable, ductile, sonorous, good conductors, high density
  • Non-metals: Dull, brittle, poor conductors, non-sonorous, low density
  • Metalloids: Properties of both (e.g., Silicon, Germanium)

Chemical Reactions

  • Metal + O2 → Basic oxide (turns red litmus blue)
  • Non-metal + O2 → Acidic oxide (turns blue litmus red)
  • Metal + Acid → Salt + H2

Exam Tips

  • Know all exceptions: Mercury (liquid), Graphite (conducts), Diamond (lustrous), Na/K (soft)
  • Learn the comparison table (8 properties) thoroughly
  • Practice writing equations for metal reactions
  • Know uses of at least 5 metals and 5 non-metals

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