Metals and Non-metals

The common name and chemical name of ores of following elements are:

(a) Mercury

(b) Iodine

(c) Carbon fibre

(d) Graphite

(e) Potassium

(a) Copper is used in :

• making electrical cables
• making utensils

(b) Iron is used in :

• construction of bridges
• making utensils, surgical instruments (in the form of stainless steel)

(c) Aluminium is used in :

• making utensils
• packaging

(d) Magnesium is used in :

• fireworks
• for making alloys called magnalium and duralumin.

(e) Zinc is used in :

• galvanization
• dry cells.

(f) Lead is used in:

• flexible pipes
• tips of bullets

(e) Silver is used in :

• making jewellery and coins
• making thin sheets to decorate sweets

Experiment to prove that a copper wire conducts electricity.

Procedure — Join a wire with the battery, copper and bulb

Observation — The bulb glows when current passes through the circuit.

Conclusion — Copper conducts electricity, hence it is a good conductor of electricity.

Experiment to prove that coal does not conduct electricity.

Procedure — Join a wire with battery, coal and bulb

Observation — The bulb does not glow.

Conclusion — Coal does not conduct electricity hence, it is a bad conductor of electricity.

Activity series of metals is a series of arrangement of metals in order of their reactivity. The most active metal is at the top of the series & the least active metal is at the bottom of the series.

Potassium is at the top of the series, hence it is the most reactive metal. It reacts vigorously even with cold water and explosively with acids to liberate hydrogen gas.

Iron lies in the middle of the series at number 7, hence it is moderately reactive. It does not react with cold water but reacts smoothly with steam and less vigorously with acids to liberate hydrogen gas.

In the Modern Periodic Table:

• Strong metals are in the extreme left, weak metals are in the middle.
• Metalloids are in the middle right.
• Non-metals are to the right in the upper right hand corner.
  • Halogens are present in Group 17 which is the second last group of the periodic table.
  • Noble gases are present in Group 18 which is the last group of the periodic table.

Reasons for keeping halogens and noble gases in separate groups of the periodic table with special reference to their properties and uses are:

1. Halogens are highly reactive non-metals. They readily react with metals to form salts. On the other hand, noble gases are inert or inactive due to their stable electronic configuration.
2. Halogens typically exist as diatomic molecules whereas noble gases are monoatomic.
3. The reactivity of halogens make them useful in variety of applications like disinfectants (chlorine), pharmaceuticals (iodine) and as non-stick coatings (fluorine derivatives), etc. The inert nature of noble gases makes them useful in neon signs (neon gas), weather balloons & cryogenics (helium), anesthesia (xenon), etc.

Metalloids are elements that show the properties of both metals and non-metals. They have physical and chemical properties, intermediate between those of metals and non-metals.

Elements like Boron [B], Silicon [Si], Germanium [Ge], Arsenic [As], Antimony [Sb], Tellurium [Te] are recognized as metalloids.

Comparison of properties:

Use of metalloids:

1. Boron — is used as an insecticide and a fire retardant.
2. Arsenic — is used for certain medicinal purposes.
3. Silicon — Silicon gel is generally applied to burn patients and to absorb moisture.

Rusting involves slow oxidation of iron in presence of air and moisture resulting in formation of hydrated iron [III] oxide called rust.

Iron + Oxygen ⟶ Iron [III] Oxide $\xrightarrow{\text{moisture}}$ Hydrated Iron [III] Oxide [rust]

Aluminium paint is anti-corrosive in nature hence it does not rust and is used to paint telegraph poles which are exposed to air and moisture.

Oiling or greasing is done on the exposed moving iron parts of machinery as it forms a coating which protects it from rusting. It smoothens the surface and reduces friction in the machinery which is its added advantage.

Being stationary, for heavy iron parts, red lead oxide paint is used as there is no use of reducing the friction.

Galvanization, tinning and chromeplating are used as three different processes because:

• In galvanization, iron sheets are dipped in molten zinc. Zinc being more active than iron, protects iron by forming zinc ions more readily. It is used for iron articles exposed to heavy moisture like roof sheds, buckets, tubs, etc.

• In tinning, iron sheets are dipped in molten tin. It is used for edible applications instead of galvanization because zinc dissolves in food acids and makes poisonous compounds.

• In chromeplating, iron articles are electroplated with chromium, nickle, tin, copper etc. It is used for decorative purposes. It is costly and used exclusively.

Hence, the three processes are different ways of preventing articles from rusting depending on their use.

(a) Rust is hydrated iron [III] oxide. As all metallic oxides are basic in nature and rust is a metallic oxide of iron, hence, it turns moist red litmus blue.

(b) The green deposit on copper articles is caused by copper reacting with moisture and atmospheric gases to form copper carbonate [CuCO₃], which is green, and copper hydroxide [Cu(OH)₂].

(c) Iron pillar of Qutab Minar has not rusted over the years because

1. The high purity and great mass of iron may have created a temperature stabilizer thus reducing the condensation of moisture on it.
2. The protective passive iron coating formation on the surface of iron.
3. Good forge welding and absence of impurities in iron.

(a) Steel in automobiles — It is malleable with high tensile strength.

(b) Gold in jewellery — It is expensive, lustrous, malleable and ductile.

(c) Copper in electrical cables — It is a good conductor of electricity.

(d) Zinc in galvanizing — It prevents rusting.

(e) Lead in bullets — It has high specific gravity.

(f) Magnesium in fireworks — It burns with a dazzling light.

1. The ability of a metal to produce a resonant sound sonority.

2. A metal which floats on water potassium.

3. A non-metal that leaves a mark on paper graphite.

4. A non-metal which allows an electric current to pass through it graphite.

5. A non-metal added to swimming pools to kill germs chlorine.

1. Metals have 1, 2 or 3 valence electrons and tend to lose one or more electrons when supplied with energy and form cations whereas non-metals have 5, 6 or 7 electrons in the valence shells and tend to gain electrons to form anions.

2. Potassium is at the top of the metal activity series making it the most reactive metal. Its high reactivity is seen in its vigorous reaction with cold water. On the other hand, copper lies towards the bottom of the series at number 10, below hydrogen. Hence, it cannot displace hydrogen from water and therefore does not react with water or steam.

3. Rusting corrodes iron thereby reducing the structural strength of iron.

4. Rust is hydrated iron [III] oxide. As all metallic oxides are basic in nature and a suspension of rust is a metallic oxide of iron, hence, it is basic in nature.

5. Galvanized steel has zinc coating and so it is not used for food containers since food acids dissolve zinc forming poisonous compounds.

1. Fluorine.

2. Aluminium.

3. Copper carbonate

4. Lead

5. Iodine

1. C: Potassium

2. A: Boron

3. B: Chlorine

4. E: Radon

5. D: Platinum

1. False
   Corrected Statement — Lead pencils contain graphite.

2. True

3. True

4. False
   Corrected Statement — (Both oxygen and moisture are essential for rusting).

5. True