Metals and Nonmetals Science Notes
Elements are classified into three types: Metals, non-metals and metalloids.
Physical properties of metals:
- Metals have a lustre.
- The metals are hard.
- They are malleable and ductile.
- Metals are good conductors of heat and electricity.
- At normal temperatures, metals are generally solids.
- Metals usually have high density.
- Metals have high melting points and boiling points.
- Metals are sonorous.
Physical properties of non-metals
- Non-metals do not have lustre.
- Non-metals are not malleable and ductile.
- They are poor conductors of heat and electricity.
- At normal temperature, non-metals are in the solid, gaseous and liquid states.
- Non-metals have low density.
- Solid non-metals are brittle.
- Non-metals have low melting and boiling points.
Metalloids have properties which are intermediate between metals and non-metals.
- Gold, Silver, Aluminium are highly malleable metals.
- A sheet with thickness 1/10,000 mm and a wire with diameter 1/5000 mm can be made from gold.
Chemical properties of metals
Majority of metals have up to three electrons in their outermost shell.
|Metal||Atomic Number||Electronic configuration|
|11Na||11||2, 8, 1|
|12Mg||12||2, 8, 2|
|13Al||13||2, 8, 3|
→ Formation of ions: Metals have a tendency to lose their valence electrons to form positively charged ions, i.e. cations.
Na → Na+ + e–
Mg → Mg++ + 2e–
A1 → A1+++ + 3e–
→ Reaction with oxygen: Metals combine with oxygen to form their oxides.
Metal + Oxygen → Metal oxide
→ The metal oxides are basic in nature. Metal oxides react with an acid to form salt and water.
Metal oxide + Acid → Salt + Water
→ Reaction with acid: Most of the metals react with dilute acids to form metal salts and hydrogen gas.
Metal + dilute Acid → Metal salt + Hydrogen gas.
→ Reaction with water: Metals like sodium and potassium react vigorously with cold water to form metal hydroxides and hydrogen gas. Magnesium metal requires steam or hot water to give their oxide and hydrogen.
Chemical properties of non-metals:
Electronic configuration: Most of the non-metals have 4 to 7 electrons in their valence shells.
|Non-Metal||Atomic Number||Electronic configuration|
|13Cl||17||2, 8, 7|
Formation of ions
Non-metals have a tendency to accept electrons in their valence shell to form negatively charged ions called anions.
Cl + e– → Cl–
0 + 2e– → 0– –
N + 3e– → N– – –
Reaction with oxygen
→ Non-metals combine with oxygen to form their oxides.
Non-metal + Oxygen → Non-metal oxide
→ The oxides of non-metals are acidic in nature. They react with bases to form soluble salt and water.
- C + O2 → C02
- C02 + 2NaOH → Na2C03 + H20
→ The oxides of non-metals react with water to form an acid.
- C02 + H20 → H2C03 Carbonic acid
- S02 + H20 → H2S03 Sulphurous acid
- S03 + H20 → H2S04 Sulphuric acid
Some metals like gold, silver, platinum, paladium and rhodium are found in nature in the form of elements. They are not affected by air, water, acids and heat etc. Hence, they are called noble metals.
→ Use of Noble metals:
- Gold, silver and platinum are used to prepare ornaments.
- Silver is used in medicines. (It has antibacterial property).
- Gold and silver are also used to make medals and few electronic devices.
- Platinum, palladium metals are used as catalyst.
Purity of gold
The purity of gold is measured in carats. 24-carat is considered as gold of 100% purity. 24-carat gold is pure and very soft. 100% pure gold bends or breaks easily. Therefore, copper or silver is added to gold in the necessary proportion while making ornaments.
Gases in the air react with metals in presence of moisture to form metal compounds on the surface. The metals get affected by this process and undergo corrosion.
There is a statue of Liberty in the sea near New York city in America. The original surface of their statues was made of copper. But now it, looks green. This is because green coloured copper carbonate has been formed by a reaction of copper with the carbon dioxide and moisture in the air. This is an example of corrosion.
There is an iron pillar in the premises of Kutubminar in Delhi, made about 1500 years ago. The pillar is lustrous even after so many years.Do you know?
→ A cheap variety of stainless steel is made sometimes by using copper instead of costly nickel. You might have seen the vertical cracks in stainless steel vessels. The reason is as above.