Metals And Non Metals Class 10 Chapter Notes | YoLearn.ai

Key Concepts: Metals and Non-metals at a Glance

• Metals are generally electropositive, forming positive ions by losing electrons, while non-metals are electronegative, forming negative ions by gaining electrons.
• Most metal oxides are basic (or amphoteric), reacting with acids to form salt and water. Non-metal oxides are acidic (or neutral).
• The reactivity series lists metals in decreasing order of their reactivity, with Potassium (K) being most reactive and Gold (Au) least reactive.
• Ionic compounds are formed by the transfer of electrons between a metal and a non-metal, creating strong electrostatic forces of attraction.
• Ionic compounds generally have high melting/boiling points, are soluble in water, and conduct electricity in molten state or aqueous solution.
• Metallurgy involves crushing, concentration (enrichment) of ore, reduction to free metal, and refining.
• Corrosion is the gradual deterioration of a material, usually a metal, by chemical reaction with its environment (e.g., rusting of iron).
• Prevention of corrosion includes painting, oiling, greasing, galvanising, chromate plating, anodising, and making alloys.

Essential Terms and Definitions

Malleability

The property of metals by which they can be beaten into thin sheets.

Ductility

The property of metals by which they can be drawn into thin wires.

Sonorous

The property of metals to produce a ringing sound when struck hard.

Amphoteric Oxides

Metal oxides that react with both acids and bases to produce salt and water (e.g., Al₂O₃, ZnO).

Reactivity Series

A list of metals arranged in the decreasing order of their reactivity.

Ionic Bond

A chemical bond formed by the complete transfer of one or more electrons from one atom to another, forming oppositely charged ions.

Gangue

Earthy or unwanted impurities present in an ore.

Roasting

Heating a sulfide ore strongly in the presence of excess air to convert it into its oxide.

Calcination

Heating a carbonate ore strongly in a limited supply of air to convert it into its oxide.

Galvanisation

The method of protecting steel and iron from rusting by coating them with a thin layer of zinc.

Metals vs. Non-metals: A Comparative View

Reactivity Series and Chemical Reactions of Metals

The reactivity series is a fundamental concept for understanding how metals react. It's an arrangement of metals in decreasing order of their chemical reactivity. The most reactive metals are at the top, and the least reactive are at the bottom.

Common Reactivity Series (from most to least reactive):
K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au

Reactions of Metals:

1. With Oxygen: Most metals combine with oxygen to form metal oxides. These are generally basic in nature. For example:

• 4Na(s) + O₂(g) → 2Na₂O(s) (Sodium oxide)
• 2Mg(s) + O₂(g) → 2MgO(s) (Magnesium oxide)

Some metal oxides, like aluminium oxide (Al₂O₃) and zinc oxide (ZnO), are amphoteric oxides as they show both acidic and basic characteristics.

1. With Water: Metals react with water to form metal oxide/hydroxide and hydrogen gas. The type of water (cold, hot, steam) depends on the metal's reactivity.

• Highly reactive metals (K, Na, Ca) react vigorously with cold water to form hydroxides and hydrogen gas. 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
• Moderately reactive metals (Mg) react with hot water to form hydroxide and hydrogen.
• Less reactive metals (Al, Zn, Fe) react with steam to form metal oxides and hydrogen gas. 2Al(s) + 3H₂O(g) → Al₂O₃(s) + 3H₂(g)
• Metals like Cu, Ag, Au do not react with water or steam.

1. With Acids: Metals generally react with dilute acids (HCl, H₂SO₄) to form a salt and hydrogen gas. Metal + Dilute Acid → Metal Salt + Hydrogen gas

• Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)
• However, copper, silver, gold do not react with dilute acids to release hydrogen as they are less reactive than hydrogen.

1. With Solutions of Other Metal Salts (Displacement Reactions): A more reactive metal can displace a less reactive metal from its salt solution. This is a direct application of the reactivity series.

• Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s) (Iron displaces copper as Iron is more reactive)
• Cu(s) + FeSO₄(aq) → No reaction (Copper cannot displace iron as it is less reactive)

Understanding Ionic Compounds

Ionic compounds are formed when electrons are transferred from a metal atom to a non-metal atom. This transfer results in the formation of positively charged ions (cations) from metals and negatively charged ions (anions) from non-metals. These oppositely charged ions are then held together by strong electrostatic forces of attraction, forming an ionic bond.

Formation of NaCl (Sodium Chloride):

• Sodium (Na) has an electronic configuration of 2, 8, 1. It readily loses its one valence electron to achieve a stable octet, forming Na⁺ ion.
• Chlorine (Cl) has an electronic configuration of 2, 8, 7. It readily gains one electron to complete its octet, forming Cl⁻ ion.
• Na⁺ and Cl⁻ ions are attracted to each other, forming NaCl.

Properties of Ionic Compounds:

1. Physical Nature: They are generally solid and somewhat hard due to the strong forces of attraction between the positive and negative ions. They are often brittle and break into pieces when pressure is applied.
2. Melting and Boiling Points: Ionic compounds have high melting and boiling points because a considerable amount of energy is required to break the strong inter-ionic attraction.
3. Solubility: They are generally soluble in water but insoluble in solvents like kerosene, petrol, etc. Water, being a polar solvent, helps to separate the ions.
4. Conduction of Electricity: Ionic compounds do not conduct electricity in the solid state because the ions are held in fixed positions. However, they conduct electricity in the molten state (fused state) and in aqueous solutions because the ions become free to move and carry charge.

Metallurgy: Extracting Metals from Ores

1. 1. Enrichment of Ores (Concentration) — Removal of unwanted impurities (gangue) from the ore. Methods include hydraulic washing, magnetic separation, froth flotation, and chemical methods.
2. 2. Extraction of Metal from Concentrated Ore — This step depends on the metal's reactivity.
3. 3. Refining of Metals — The extracted metal is often impure and needs purification. The most common method is electrolytic refining, where the impure metal acts as the anode, pure metal as the cathode, and a salt solution of the metal as the electrolyte.

Corrosion and its Prevention

Corrosion is the process of slow eating up of the surface of metals due to the attack of atmospheric gases and moisture. The most common example is the rusting of iron, where iron reacts with oxygen and moisture to form hydrated iron(III) oxide (Fe₂O₃.xH₂O), which is reddish-brown and flaky.

Conditions for Rusting: Presence of both oxygen (air) and water (moisture).

Prevention of Corrosion:

• Painting, Oiling, Greasing: These methods prevent the metal surface from coming into contact with air and moisture.
• Galvanising: Coating iron or steel with a thin layer of zinc. Zinc is more reactive than iron, so it corrodes preferentially, protecting the iron (sacrificial protection).
• Chromium Plating: Coating with chromium, which is corrosion-resistant and gives a shiny appearance.
• Anodising: An electrolytic process that creates a thick oxide layer on aluminium, making it more corrosion-resistant and often dyed for decorative purposes.
• Making Alloys: Mixing metals with other metals or non-metals to improve properties, including corrosion resistance (e.g., stainless steel is an alloy of iron with nickel and chromium, which is highly resistant to rusting).

Exam Tip: Reactivity Series and Ionic Bonds

Pay close attention to the reactivity series! Many questions revolve around predicting reaction outcomes (displacement reactions) or explaining why certain metals react in specific ways with water or acids. Memorise the order. For ionic compounds, focus on how they are formed (electron transfer) and why their properties (high melting point, conductivity in molten/aqueous state) are distinct. Be ready to draw electron dot structures for simple ionic compounds like NaCl, MgCl₂, Na₂O, and MgO.

Quick Revision Check

• Q: Why is sodium stored under kerosene oil? A: Sodium is a highly reactive metal. It reacts vigorously with oxygen, carbon dioxide, and moisture present in the air, often catching fire. Storing it under kerosene prevents its contact with air and moisture.
• Q: What are amphoteric oxides? Give an example. A: Amphoteric oxides are metal oxides that show both acidic and basic properties, meaning they react with both acids and bases to produce salt and water. Example: Aluminium oxide (Al₂O₃) or Zinc oxide (ZnO).
• Q: Why do ionic compounds conduct electricity in molten state but not in solid state? A: In the solid state, ions in ionic compounds are held in fixed positions by strong electrostatic forces, so they cannot move. In the molten (fused) state or aqueous solution, the ions become free to move and thus can carry electric charge, allowing conduction.
• Q: Name two methods to prevent rusting of iron. A: Two methods are: galvanisation (coating with zinc) and painting. Other methods include oiling, greasing, and making alloys like stainless steel.

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