Properties of metals

Properties of metals

Physical properties

we are only going to discuss a few Properties of metals.

Good conductors of electricity since they have delocalised electrons in their giant metallic structure

High melting and boiling points due to strong metallic bonds within the giant metallic structure

Density is determined by atomic size, packing of the atoms in the metallic lattice and the atomic masses

Most metals are malleable (can be hammered into sheets) and ductile (can be drawn into wires)




Chemical properties

Reaction with air

Sodium

Rapidly tarnishes in dry air forming sodium oxide

2 Na (s)  +   O2 (g) → 2 Na2O (s)

In moist air both sodium metal and the oxide react with air to form its hydroxide

2 Na (s) + 2H2O (l)   → 2NaOH (aq)   +       H2 (g)

Na2O (s) +   2H2O (l)  → 2NaOH (aq)

The resulting alkali absorbs carbon (IV) oxide in the air to form sodium carbonate

2 NaOH (aq) + CO2 (g) → Na2CO3 (aq) + H2 O(l)

Sodium burns in air with a yellow flame forming mainly sodium peroxide

2 Na (s)  +   O2 (g)  →  2Na2O2(s)

 Zinc

Tarnishes slowly in air forming zinc oxide

When heated it burns forming smoke of zinc oxide which is poisonous

2 Zn (s)  +  O2 (g)   → 2ZnO(s)

 Polished aluminium is immediately coated with a layer of aluminium oxide

If heated to about 800oC it burns to form aluminium oxide and aluminium nitride

4Al (s) +  3O2 (g)   → 2Al2O3(s)

2 Al (s) + N2 (g)   → 2AlN(s)

Iron forms rust in presence of oxygen and air

4Fe(s) +2H2O (l)) +  3O2 (g)   → 2Fe2O3 . H2O(s)

When it is heated it glows forming tri iron tetraoxide

3 Fe (s)  +  2O2 (g) → Fe3O4(s)

Copper forms a black coat of copper (II) oxide

Finely divided copper burns with blue flame

2 Cu (s)   +      O2 (g) →  2CuO(s)




Reaction with cold water and steam

Sodium reacts vigorously with cold water forming hydrogen gas and sodium hydroxide solution which is alkaline

2 Na (s)  + 2H2O (l)  → 2NaOH (aq)   +    H2 (g)

Zinc and iron do not readily react with cold water

Aluminium does not react with cold water due a protective layer of aluminium oxide but if cleaned it racts ver y slowly

2Al (s) + 6H2O (l) → 2Al (OH) 3 (s)   + 3H2 (g)

Copper does not react with cold water

Aluminium, zinc and react with steam to form their oxides

2 Al (s)  +   3H2O (g) → Al2O3 (s) +  3H2 (g)

Zn (s)  +   H2O (g) → ZnO (s)   +  H2 (g)

3 Fe(s)  +  4H2O (g) →Fe3O4 (s)  +     4H2 (g)

Copper does not react with steam

Reaction with chlorine

All the metals react with chlorine to form their chlorides

2 Na (s)  + Cl2 (g)  → 2NaCl (s)

2 Fe (s)  + 3Cl2 (g) → 2FeCl3 (s)

2 Al (s)  + 3Cl2 (g) → 2AlCl3 (s)

Cu (s)  + Cl2 (g)  → CuCl2(s)

Iron (III) chloride and aluminium chloride fume when exposed to dump air since the water forming hydrogen chloride gas

AlCl3 (s)  + H2O (l) → Al (OH) 3 (s) + 3 HCl (g)

FeCl3 (s)  + H2O (l)  → Fe (OH) 3 (s) + 3 HCl (g)

Reaction with acids

Aluminium when polished reacts slowly with dilute hydrochloric acid to liberate hydrogen gas and form aluminium chloride

2HCl (s)  +   6HCl (aq)  → 2AlCl3 (aq)    + 3H2 (g)

There is no reaction between aluminium and nitric (V) acid or sulphuric (VI) acid

Nitric (V) acid is a strong oxidising agent and immediately forms a thin coat of aluminium oxide immediately it comes into contact with aluminium preventing further reaction



Aluminium reduces hot concentrated sulphuric (VI) acid to sulphur and itself oxidised to aluminium sulphate

2Al (s) + H2SO4 (l) →Al2SO4 (aq)    +     6H2O (l)    +   3SO2 (g)

Iron reduces hot concentrated sulphuric (VI) acid to sulphur (IV) oxide

2Fe (s) +6H2SO4 (l) →Fe2 (SO4)3 (aq) +   6H2O (l)    +   3SO2 (g)

Iron does not react with concentrated nitric (V) acid. The concentrated nitric oxidises iron into an impervious layer of tri-iron tetra oxide preventing further reaction

Zinc reduces both concentrated nitric (V) acid and concentrated sulphuric (VI) acid to nitrogen (IV) oxide and sulphur (IV) oxide respectively

Copper reacts in a similar way

Zn (s) + 2H2SO4 (l) → ZnSO4 (aq)    +     2H2O (l)    +   SO2 (g)

Cu (s) + 2H2SO4 (l)  → CuSO4 (aq)    +    2H2O (l)   +   SO2 (g)

2Cu (s) +4HNO3 (l) →Cu (NO3)2 (aq) + 2H2O (l)   + 2NO2 (g)

2Zn (s)  + 4HNO3 (l) → Zn (NO3)2 (aq)  +  2H2O (l)  + 2NO2 (g)

With 50% dilute nitric (V) acid nitrogen (II) oxide is formed

3Cu (s) + 8HNO3 (l) → Cu (NO3)2 (aq) + 4H2O (l)    + 2NO (g)

3Zn (s) + 8HNO3 (l) → Zn (NO3)2 (aq)  + 4H2O (l)  + 2NO (g)

Zinc and iron react with dilute acids forming salt and hydrogen gas

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METALS WORD FILE