Metallurgy
Position and characteristics of s block elements
Alkali metals and alkaline earth metals are found in the s block of the periodic table.
1. Occurrence: These metals occur naturally as carbonates, sulphides, oxides or halides in
the earth’s crust and these are called minerals. They are very reactive and hence cannot be
found free in nature.
2. Nature: Soft, low boiling and melting points, silvery white in colour, lustrous
3. Bonding: Ionic in nature, form electrovalent compounds. Alkali metals form uni-positive
ions (M+) and alkaline earth metals form bi positive ions (M2+).
Chemical reactions of s block elements
Reaction with Reaction with
Metal Reaction with water
oxygen acids
React violently with cold
Vigorous
(Alkali water. Highly exothermic
reaction- catch React extremely
metals) reaction. Released hydrogen
fire if exposed violently with rapid
Sodium immediately catches fire
to air, hence effervescence and
and K+H2O→2KOH +H2↑+heat
stored under splashing
Potassium Na+H2O→2NaOH+H2↑+hea
kerosene
t
Burns Less violent reaction with Reacts readily to
(alkaline
vigorously to water, heat evolved not form chloride salt
earth
form oxide enough for H2 to catch fire Ca
metal)
2Ca+O2→2Ca Ca+2H2O→Ca(OH)2 +H2↑ +2HCl→CaCl2+H2
Calcium
O Ca starts floating as bubbles ↑
of H2 stick to metal surface
Reacts with hot water, starts
floating due to H2 bubbles
, Magnesiu At room sticking to it React readily to
m temperatures, Mg + 2H2O→ Mg(OH)2+H2↑ form salt and
surface is hydrogen
coated by thin Mg + HCl→
oxide layer MgCl2+H2 ↑
which prevents
further
oxidation
Differences between metal and non-metals:
Physical properties
Metals Non-metals
Malleable (can be beaten into sheets) Non-malleable
Ductile (can be drawn into wires) Non-ductile
Lustrous (shining surface) Non-lustrous (except iodine)
Sonorous (make a ringing sound) Non-sonorous
Brittle, break easily, low density (except
High density (except sodium,
diamond which is the hardest substance
potassium which can be cut by knife)
known)
Good conductors of heat and Poor conductors of heat and electricity except
electricity (except lead and mercury) graphite which is a good conductor
Position and characteristics of s block elements
Alkali metals and alkaline earth metals are found in the s block of the periodic table.
1. Occurrence: These metals occur naturally as carbonates, sulphides, oxides or halides in
the earth’s crust and these are called minerals. They are very reactive and hence cannot be
found free in nature.
2. Nature: Soft, low boiling and melting points, silvery white in colour, lustrous
3. Bonding: Ionic in nature, form electrovalent compounds. Alkali metals form uni-positive
ions (M+) and alkaline earth metals form bi positive ions (M2+).
Chemical reactions of s block elements
Reaction with Reaction with
Metal Reaction with water
oxygen acids
React violently with cold
Vigorous
(Alkali water. Highly exothermic
reaction- catch React extremely
metals) reaction. Released hydrogen
fire if exposed violently with rapid
Sodium immediately catches fire
to air, hence effervescence and
and K+H2O→2KOH +H2↑+heat
stored under splashing
Potassium Na+H2O→2NaOH+H2↑+hea
kerosene
t
Burns Less violent reaction with Reacts readily to
(alkaline
vigorously to water, heat evolved not form chloride salt
earth
form oxide enough for H2 to catch fire Ca
metal)
2Ca+O2→2Ca Ca+2H2O→Ca(OH)2 +H2↑ +2HCl→CaCl2+H2
Calcium
O Ca starts floating as bubbles ↑
of H2 stick to metal surface
Reacts with hot water, starts
floating due to H2 bubbles
, Magnesiu At room sticking to it React readily to
m temperatures, Mg + 2H2O→ Mg(OH)2+H2↑ form salt and
surface is hydrogen
coated by thin Mg + HCl→
oxide layer MgCl2+H2 ↑
which prevents
further
oxidation
Differences between metal and non-metals:
Physical properties
Metals Non-metals
Malleable (can be beaten into sheets) Non-malleable
Ductile (can be drawn into wires) Non-ductile
Lustrous (shining surface) Non-lustrous (except iodine)
Sonorous (make a ringing sound) Non-sonorous
Brittle, break easily, low density (except
High density (except sodium,
diamond which is the hardest substance
potassium which can be cut by knife)
known)
Good conductors of heat and Poor conductors of heat and electricity except
electricity (except lead and mercury) graphite which is a good conductor
