Importance:
The chapter on "Metals and non-metals" is assigned a weightage of \(10\) marks, highlighting its significance in the overall curriculum. Understanding this chapter will enhance the understanding of the properties, reactions, and uses of metals and non-metals.
Question distribution:
- Section A (\(1\) mark) - One question
- Section B (\(2\) mark) - One question
- Section C (\(3\) mark) - One question
- Section E (\(4\) mark) - One question
(Note: The exact mark distribution may vary slightly across examinations.)
Learning objectives:
-
Physical properties of metals and non-metals: Understand and differentiate the key physical properties of metals and non-metals with exceptions.
-
Chemical reactions of metals and non-metals with water, oxygen, and acids: Explore how metals and non-metals react with water, oxygen, and acids, including the reaction process, rate, and products formed.
-
Reactivity of metals and non-metals and ionic properties: Know the reactivity patterns of metals and non-metals in detail and examine the fundamental properties of ionic compounds.
-
Metallurgy and corrosion: Learn about the occurrence of metals, methods of ore enrichment, and extraction processes across the activity series. Additionally, to understand corrosion, its causes, and preventive measures.
Physical properties of metals and non-metals:
| Property | Metals | Non-metals |
| Physical state |
Mostly solid at room temperature
Exception: Hg, Cs, Ga - Liquid near room temperature
|
Exist in all three states
Exception: Br - only liquid non-metal
|
| Lustre | Lustrous |
Dull
Exception: Iodine, graphite and diamond
|
| Hardness |
Mostly hard
Exception: Na, K, Li - Soft
|
Generally soft
Exception: Diamond (allotrope of carbon)
|
| Density |
High
Exception: Alkali metals (Li, Na, K)
|
Low
Exception: Diamond
|
| Melting and boiling point |
High
Exception: Hg, Cs, Ga, Na, K, Li
|
Low
Exception: Diamond
|
| Malleability and ductility |
Malleable and ductile
Exception: Hg
|
Brittle
|
| Conductivity |
Good conductor of heat and electricity
Silver - Best conductor
Exception: Lead and mercury (Heat)
|
Poor conductor of heat and electricity
Exception: Graphite
|
| Sonority |
Sonorous
Exception: Hg
|
Non-sonorous |
PYQ - Reaction of metals
Chemical properties of metals and non-metals:
1. Reaction of metals with oxygen:
Metals react with oxygen to form basic oxides.
\(2Mg + O_2 → 2MgO\)
\(MgO + H_2O → Mg(OH)_2\)
Reaction of non-metals with oxygen:
Non-metals react with oxygen to form acidic oxides.
\(S + O_2 → SO_2\)
\(SO_2 + H_2O → H_2SO_3\)
Amphoteric oxides: Oxides behaving as both acid and base. Example: \(Al_2O_3\) and \(ZnO\)
Reactivity order:
\(K > Na > Mg > Al > Zn > Fe > Pb > Cu\)
PYQ - Amphoteric oxides, Metal oxides
2. Reaction of metals with water:
|
Metals
|
Reaction with normal water
|
Reaction with cold water
|
Reaction with hot water
|
Reaction with steam
|
Catches fire
|
Floats on water
|
| Na, K | __ |
Yes
|
__
|
__
|
Yes
|
__
|
|
Ca
|
Yes
|
__
|
__
|
__
|
__
|
Yes
|
|
Mg
|
__
|
__
|
Yes
|
__
|
__
|
Yes
|
|
Al, Fe, Zn
|
__
|
__
|
__
|
Yes
|
__
|
__
|
|
Pb, Cu, Ag, Au
|
__
|
__
|
__
|
__
|
__
|
__
|
Decreasing order of reactivity with water:
\(K> Na > Ca > Mg > Al > Fe > Pb > Cu > Ag > Hg\)
Most of the non-metals do not react with water.
3. Reaction of metals with acids:
Most reactive metals react with acids to form salt and hydrogen gas
\(Zn + 2HCl → ZnCl_2 + H_2\)
The metals placed below hydrogen atom in the reactivity series will not react with acids.
Exception:
\(HNO_3\) is a powerful oxidising agent. By oxidising the \(H_2\) generated to water, it reduces itself to any of the nitrogen oxides (\(N_2O\), \(NO\), \(NO_2\)).
Magnesium (\(Mg\)) and manganese (\(Mn\)) react with very dilute \(HNO_3\) to produce \(H_2\) gas. The reaction was also the highly exothermic.
Aqua regia \(= 3 HCl : 1 HNO_3\)
It is the only acidic mixture that dissolves gold and platinum, which do not react with \(HCl\) or \(HNO_3\) alone.
It is the only acidic mixture that dissolves gold and platinum, which do not react with \(HCl\) or \(HNO_3\) alone.
Reactivity series (Activity series):
Most Reactive → Least Reactive
\(K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au\)