Non Metals and the Periodic table
Formation of Non-metal Oxides
The inert gases have full electron shells and are therefore almost unreactive. The gases are:
Helium Neon Argon Krypton Xenon Radon
Other non-metals have a strong attraction for electrons from other atoms. This is because their outer electron shell is not quite full. This means they gain extra electrons and form negative ions.
Nitrogen is very unreactive and forms 78% of the air we breathe. Under very high temperatures it burns in oxygen.
Nitrogen + Oxygen —> Nitrogen Oxide
N2 + O2 –> 2NO
The NO burns again in oxygen from air to form nitrogen dioxide:
2NO + O2 —> NO2
This is a toxic gas which is brown in colour. It can form from the engines of cars.
Sulfur is a brittle yellow solid and is found in nature as 58 rings. It burns in air:
Sulfur + Oxygen —> Sulfur Dioxide
S + O2 —> SO2
Sulfur dioxide will then burn further to sulfur trioxide:
SO2 + O2 —> SO3
If the sulfur trioxide dissolves in water it forms sulfuric Acid
SO3 + H2O —> H2SO4
This whole process is how acid rain forms. The sulfur can be present in coal and/or oil when it is burnt.
Carbon is a solid element. It forms two allotropes in nature: graphite and diamond. Soot or
charcoal is another form of carbon. Carbon forms two products when it burns: carbon monoxide (CO)
and carbon dioxide (CO2).
Complete combustion in plentiful air:
C + O2 —> CO2
CO2 is colourless and odourless. It doesn’t support burning and for example, is used in fire
Incomplete combustion in a lack of air:
2C + O2 —> 2C0
CO is also a colourless, odourless gas but is highly toxic. It can form in engines when a fuel is burnt.
Acidic Properties of Non-metal Oxides
Soluble metal oxides form acidic solutions when they dissolve in water.
- Nitrogen dioxide. Dissolves in water to form
- Sulfur dioxide. Dissolves in water to form
- Carbon dioxide. Dissolves in water to form
The amount these oxides dissolve in water varies,
e.g. sulfur dioxide dissolves easily whereas carbon
dioxide only dissolves slightly.
Examples of these processes are:
• Nitrogen and sulfur both can form acid rain.
• Carbon dioxide dissolved in water over extremely long periods of time will react
with limestone to form caves.
Common Household Acids
Common acids around the household are:
– Acetic acid found in vinegar.
– Citric acid found in citrus fruits like lemons and oranges.
– Tartaric acid is used in cooking and purchased from supermarkets.-
– Sulfuric acid is the acid used in a car battery.
The pH of acids is less than 7. Acids release H+ ions when dissolved in solution.
- The organic acids are: acetic acid, citric acid and tartaric acid. These acids are mild in strength but have a bitter and sour taste.
- Sulfuric acid is a non-metal acid that is extremely corrosive. It can react very quickly with, for example, iron or aluminium.
Common Household Bases
Common bases around the household are:
– Ammonium hydroxide Found in household cleaners.
– Sodium hydroxide Found in oven cleaners and is a product for cleaning blocked drains.
– The bases neutralise the acids, have a soapy feel and are bitter to taste.
– The pH of bases is greater than 7. Bases can be very corrosive. Caustic soda is a very corrosive base
and care must be taken with its handling.
Bases remove H+ ions from solution. Bases can neutralise acids. The reaction is:
Base + Acid —> Salt + Water
This is called a neutralisation reaction.