From the pan to the plate, also from the fire to the food - our whole meal is a teamwork of metals and non-metals. Without which we couldn’t even boil water!
- Mostly metals are generally hard, shiny and good conductors of heat and electricity.
- Mostly non-metals may be solid, liquid or gas and are generally poor conductors.
Let’s learn about the metals and non-metals that we rely on in our daily lives.
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 |
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 \(ZnO\)
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
|
__
|
__
|
__
|
__
|
__
|
__
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Decreasing order of reactivity with water:
\(K> Na > Ca > Mg > Al >Zn > Fe > Pb > Cu > Ag > Hg \)
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.
Aquaregia \(= 3 HCl : 1 HNO_3\)
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
\(K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au > Pt\)
Ionic compounds (Transfer of electrons):
| Type of element | Valence electrons |
| Metals | 1, 2, and 3 |
| Non-metals | 5, 6 and 7 |
Metal + non-metal → Ionic bond (or) electrovalent bond
Metal: Loss of electron - Cation (\(+\))
Non-metal: Gain of electron - Anion (\(-\))
Non-metal: Gain of electron - Anion (\(-\))
Examples: \(NaCl\), \(MgCl_2\), \(Na_2O\), \(MgO\) and \(AlCl_3\)
Formation of \(MgCl_2\):
- Magnesium atom: Electrons present = \(12\), Electronic configuration = (\(2, 8, 2\))
- Chlorine atom: Electrons present = \(17\), Electronic configuration = (\(2, 8, 7\))
- Cation: \(Mg^{2+}\)
- Anion: \(Cl^-\)
Magnesium chloride formation
Properties of ionic compounds:
- Physical state: Crystalline solids. Strong force of attraction between ions.
- High melting and boiling points: Large amount of energy is required to break inter-ionic forces
- Solubility: Soluble in polar solvents (water); Insoluble in non-polar solvents
- Conductivity: Do not conduct electricity in a solid state → ions are fixed. Conduct in molten state or aqueous solution → ions become free to move.
Occurrence of metals:
High reactive metals (\(K, Na, Ca, Mg, Al\))
-
Never found free
-
Strong affinity for oxygen
-
Extracted by electrolysis
Moderate reactive metals (\(Zn, Fe, Pb, Cu\))
-
Found as oxides, sulphides, carbonates
-
Extracted by roasting/calcination \(+\) reduction
Low reactive metals (Ag, Au, Pt)
-
Found native (free)
-
Often require simple heating
Ores extracted from the earth usually contain large amounts of impurities such as soil, sand, etc., called gangue. Impurities must be removed from the ore before the metal can be extracted.
Extraction of metals based on reactivity:
Extraction of metals
Thermit reaction:
\(Fe_2O_3(s) +2Al(s) → 2Fe(l) + Al_2O_3(s) +\ heat\)
Type of reaction: Displacement and exothermic
Application: Joining railway tracks, cracked machine parts and welding
Electrolytic refining:
Copper, zinc, tin, nickel, silver, gold and other metals are purified electrolytically.
Refining of metals
Corrosion:
Corrosion is the progressive destruction of metals by the action of air, moisture or chemicals (such as an acid) on their surface.
| Metal | Reaction | Colour of the product |
| Silver | \(Ag + S → Ag_2S\) | Black (Tarnish) |
| Copper | \(Cu + H_2O + CO_2 → CuCO_3\) | Green (Patina) |
| Iron | \(Fe + O_2 + H_2O → 2Fe_2O_3.xH_2O\) | Reddish brown (Rust) |
Alloys:
A homogeneous mixture of metals (or metals + non-metals) to improve properties.
| Alloy | Composition | Uses |
| Brass | \(Cu + Zn\) | Decorative items, instruments |
| Bronze | \(Cu + Sn\) | Statues, tools and medals |
| Solder | \(Pb + Sn\) | Joining electrical components, plumbing etc |
| Amalgam | \(Metals + Hg\) | Dental fillings |
| Stainless Steel | \(Fe + Cr + Ni\) | Utensils, medical tools |
| Gold Alloy |
\(Au + Cu/Ag\)
22 parts gold + 2 parts Cu/Ag
|
Harder than pure gold; used in jewellery |