3.1 PHYSICAL PROPERTIES

1 Metals

Metals possess a set of characteristic physical properties that distinguish them from non-metals. These properties arise mainly due to the presence of metallic bonding, where free electrons move within a lattice of positively charged metal ions.

1. Lustre
   - Metals have a shiny appearance or metallic lustre.
   - Reason: Free electrons reflect light from the metal surface, giving it a bright and polished look.
   - Example: Gold, silver, and copper shine brightly when polished.
2. Malleability
   - Metals can be beaten into thin sheets without breaking.
   - Reason: Layers of metal atoms can slide over each other without breaking metallic bonds.
   - Example: Aluminium and gold can be hammered into foils.
3. Ductility
   - Metals can be drawn into thin wires.
   - Reason: Metallic bonds are strong yet flexible, allowing atoms to move without the structure breaking.
   - Example: Copper and silver are highly ductile metals.
4. Conductivity
   - Metals are good conductors of heat and electricity.
   - Reason: Free electrons in the metallic structure can move easily, transferring energy or electric charge.
   - Example: Copper and aluminium are used in electrical wires.
5. High Density
   - Most metals have high density, meaning they are heavy for their size.
   - Reason: Metal atoms are closely packed in a regular lattice.
   - Example: Iron, gold, and platinum have high densities.
6. High Melting and Boiling Points
   - Metals generally have high melting and boiling points.
   - Reason: Strong metallic bonds require large amounts of energy to break.
   - Exception: Mercury is a liquid metal at room temperature.
7. Hardness
   - Most metals are hard, though some (like sodium and potassium) are soft and can be cut with a knife.
   - Example: Iron is hard, whereas sodium is soft.
8. Sonorous Nature
   - Metals produce a ringing sound when struck.
   - Example: Bells and musical instruments are made of metals such as copper and bronze.
9. Solid State
   - Except for mercury, all metals exist as solids at room temperature.
   - Example: Iron, aluminium, and zinc are solid metals.
10. Appearance and Colour
    - Most metals are greyish or silvery in colour.
    - Exceptions: Gold is yellow, and copper is reddish-brown.

2 Non-metals

Non-metals are elements that generally show properties opposite to those of metals. They are found on the right side of the periodic table (except Hydrogen). Their physical properties vary widely, but the following characteristics are common:

1. State: Most non-metals are gases (e.g., oxygen, nitrogen, chlorine), some are solids (e.g., sulfur, carbon, phosphorus), and bromine is a liquid at room temperature.
2. Lustre: Non-metals are non-lustrous (dull) and do not have a shiny surface. However, iodine is an exception—it has a metallic lustre.
3. Hardness: Non-metals are usually soft and brittle (when solid). Diamond, a form of carbon, is an exception as it is the hardest known natural substance.
4. Density: They generally have low density compared to metals.
5. Melting and Boiling Points: Non-metals have low melting and boiling points, though carbon (diamond and graphite) have very high melting points.
6. Conductivity: Non-metals are poor conductors of heat and electricity, except graphite, which is a good conductor due to the presence of free electrons.
7. Malleability and Ductility: They are neither malleable nor ductile; instead, they break easily when hammered or stretched.
8. Appearance: Non-metals often have varied colors and are not metallic in appearance.

3.2 CHEMICAL PROPERTIES OF METALS

Chemical Properties of Metals

Metals show characteristic chemical behaviors that distinguish them from non-metals. Below are the main chemical properties of metals:

1. Reaction with Oxygen
   - Metals react with oxygen to form metal oxides.
   - Metal+Oxygen→Metal Oxide
   - Example:
      4Na+O2​→2Na2​O
      2Mg+O2​→2MgO
   - Most metal oxides are basic in nature (they react with acids to form salt and water).
   - Example:
      MgO+2HCl→MgCl2​+H2​O
   - Some metal oxides like zinc oxide (ZnO) and aluminium oxide (Al₂O₃) are amphoteric (they react with both acids and bases).
2. Reaction with Water
   - Some metals react with water to form metal hydroxides and hydrogen gas.
   - Metal+Water→Metal Hydroxide+Hydrogen
   - Example:
     2Na+2H2​O→2NaOH+H2​↑
   - Metals like potassium and sodium react violently with water.
   - Magnesium reacts slowly with hot water, while iron reacts only with steam.
   - Copper, silver, and gold do not react with water.
3. Reaction with Acids
   - Metals react with dilute acids to produce a salt and hydrogen gas.
   - Metal+Acid→Salt+Hydrogen
   - Example:
     Zn+2HCl→ZnCl2​+H2​↑
   - However, copper, silver, and gold do not react with dilute acids.
4. Reaction with Bases
   - Some metals react with strong bases like sodium hydroxide (NaOH) to form complex salts and hydrogen gas.
   - Example:
     2Al+2NaOH+6H2​O→2Na[Al(OH)4​]+3H2​↑
5. Displacement Reactions
   - A more reactive metal can displace a less reactive metal from its compound.
   - Metal1​+Salt of Metal2​→Metal1​Salt+Metal2​
   - Example:
     Zn+CuSO4​→ZnSO4​+Cu
   - This shows the reactivity series of metals.
   
   

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