Class 10 Science Notes Chapter 3: Metals and Non-metals

Metals and non-metals are the two major categories of elements based on their physical and chemical properties. From the utensils we use every day to the wires that carry electricity, metals play an essential role in our lives, while non-metals are equally important in processes such as respiration, agriculture and manufacturing. This chapter explains how metals and non-metals differ, how they react with oxygen, water, acids and salt solutions and why some metals are more reactive than others.

These concise Class 10 Science Notes Chapter 3 Metals and non-metals are to help students revise the chapter quickly while understanding the concepts in a simple and exam-oriented manner. 

Topics Covered in Class 10 Science Notes Chapter 3 Metals and Non-Metals

Class 10 Science Chapter 3: Metals and Non-Metals

What are Metals and Non-Metals

Elements are classified into metals and non-metals based on their physical and chemical properties.

Metals are generally hard, shiny, strong and good conductors of heat and electricity. Examples include iron, copper, aluminium and zinc.Non-metals are usually dull, brittle (if solid) and poor conductors of heat and electricity. Examples include oxygen, sulphur, carbon and nitrogen

While most elements fit these characteristics, a few exceptions exist. For example, graphite (a form of carbon) conducts electricity and iodine is lustrous despite being a non-metal.

Occurrence and Extraction of Metals

Metals occur naturally as minerals and ores. Ores are minerals from which metals can be extracted economically.

Common Steps in Metal Extraction

1. Concentration of ore:Removal of impurities (gangue).
2. Roasting or Calcination:Conversion of sulphides or carbonates into oxides.
3. Reduction:Metal oxide is converted into metal using carbon or electrolysis.
4. Refining: Purification of the extracted metal by electrolytic refining.

Physical Properties of Metals

Metals possess several unique physical properties that make them useful in everyday life.

Property	Description
Lustre	Metals have a shiny surface.
Malleability	They can be beaten into thin sheets.
Ductility	They can be drawn into wires.
Conductivity	Metals conduct heat and electricity efficiently.
Sonority	They produce a ringing sound when struck.
Hardness	Most metals are hard and strong.

Exceptions

• Mercury is the only metal that is liquid at room temperature.
• Sodium and potassium are soft enough to be cut with a knife.
• Gallium and caesium have low melting points.
• Gold and silver are the most malleable metals.
• Gold is also the most ductile metal.

Chemical Properties of Metals

Metals undergo different chemical reactions depending on the substance they react with.

1. Reaction with Oxygen

Most metals combine with oxygen to form metal oxides, which are basic in nature.

Example

$2Cu + O_2 \rightarrow 2CuO$

Some metal oxides such as aluminium oxide and zinc oxide are amphoteric, meaning they react with both acids and bases.

2. Reaction with Water

Highly reactive metals such as sodium and potassium react violently with cold water to produce metal hydroxides and hydrogen gas.

$2Na + 2H_2O \rightarrow 2NaOH + H_2$

Magnesium reacts with hot water, while aluminium, zinc and iron react with steam. Copper, silver and gold do not react with water.

3. Reaction with Acids

Reactive metals react with dilute acids to produce a salt and hydrogen gas.

$Zn + 2HCl \rightarrow ZnCl_2 + H_2$

Copper, silver and gold do not react with dilute hydrochloric acid. Nitric acid behaves differently because it is a strong oxidising agent.

4. Reaction with Salt Solutions

A more reactive metal displaces a less reactive metal from its salt solution.

Example:

$Fe + CuSO_4 \rightarrow FeSO_4 + Cu$

This is known as a displacement reaction.

Occurrence of Non-Metals

Non-metals occur in nature in both the free state and the combined state, depending on their reactivity. Less reactive non-metals such as oxygen, nitrogen, sulphur, carbon and the noble gases are found in their elemental form. 

More reactive non-metals, including hydrogen, chlorine, and phosphorus, are commonly found as compounds in water, minerals, rocks and living organisms.

Common Sources of Non-Metals

Non-Metal	Natural Occurrence
Oxygen	Atmosphere, water
Nitrogen	Atmosphere
Carbon	Diamond, graphite, carbonates
Hydrogen	Water, hydrocarbons
Chlorine	Sodium chloride (rock salt, seawater)
Phosphorus	Phosphate minerals

Physical Properties of Non-Metals

Non-metals generally exhibit properties opposite to those of metals.

• They are usually dull in appearance.
• Most are brittle and cannot be beaten into sheets.
• They are poor conductors of heat and electricity.
• They are not sonorous.
• Many non-metals exist as gases, while bromine is the only liquid non-metal.

Exceptions

• Graphite conducts electricity.
• Diamond is one of the hardest natural substances.
• Iodine has a shiny appearance.

Chemical Properties of Non-Metals

Non-metals exhibit chemical properties that are generally opposite to those of metals. Instead of losing electrons, they usually gain electrons during chemical reactions to form negatively charged ions (anions). 

1. Reaction with Oxygen

Non-metals react with oxygen to form acidic or neutral oxides.

• Acidic oxides dissolve in water to form acids.
• Neutral oxides do not show acidic or basic behaviour.

Examples

$C + O_2 \rightarrow CO_2$

$S + O_2 \rightarrow SO_2$

Carbon dioxide and sulphur dioxide are acidic oxides.

2. Reaction with Hydrogen

Many non-metals combine with hydrogen to form covalent compounds known as hydrides.

Examples

$H_2 + Cl_2 \rightarrow 2HCl$

$N_2 + 3H_2 \rightarrow 2NH_3$

These compounds have important industrial and biological applications.

3. Reaction with Metals

Non-metals react with metals by gaining electrons to form ionic compounds.

Example

$2Na + Cl_2 \rightarrow 2NaCl$

In this reaction, sodium loses electrons while chlorine gains electrons, resulting in the formation of sodium chloride.

4. Reaction with Acids

Unlike metals, non-metals generally do not react with dilute acids and therefore do not displace hydrogen gas from acids.

For example, carbon and sulphur do not react with dilute hydrochloric acid to produce hydrogen.

5. Electron Gain

Non-metals have high electronegativity and tend to gain electrons to achieve a stable electronic configuration.

Example

$Cl + e^- \rightarrow Cl^-$

This tendency to gain electrons makes non-metals good oxidising agents in many chemical reactions.

Reactivity Series

The reactivity series arranges metals in decreasing order of their chemical reactivity.

K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au

Importance of Reactivity Series 

• Predicts displacement reactions.
• Helps identify the method of metal extraction.
• Explains reactions with oxygen, water and acids.
• Indicates whether a metal can displace hydrogen from acids.

Ionic Compounds

Ionic compounds are formed when electrons are transferred from a metal to a non-metal. The metal forms a positive ion (cation), while the non-metal forms a negative ion (anion).

Properties of Ionic Compounds

• Hard and brittle solids
• High melting and boiling points
• Soluble in water
• Insoluble in kerosene and petrol
• Conduct electricity only in molten or aqueous states because ions are free to move

Corrosion and Prevention

Corrosion is the gradual deterioration of metals due to reactions with air and moisture. Rusting of iron is the most common example.

Methods to Prevent Corrosion

• Painting
• Oiling and greasing
• Galvanisation (zinc coating)
• Anodising (for aluminium)
• Alloying, such as making stainless steel