Chemistry Topic
Ionic and Covalent Compounds
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Study focus - 3 things
- Ionic compounds are made of positive and negative ions in a fixed ratio
- Covalent compounds are made when non-metal atoms share electrons
- Properties help you tell compound types apart in exam questions
Section 1What a compound is
A compound is a pure substance made when two or more different elements are chemically joined. The elements are not just mixed; they are bonded. Sodium chloride, the salt used in many Jamaican kitchens, is a compound.
Section 2Ionic compounds
Ionic compounds contain positive and negative ions arranged together. They often have high melting points and can conduct electricity when molten or dissolved in water. Solid ionic compounds usually do not conduct because the ions cannot move freely.
Section 3Covalent compounds
Covalent compounds contain atoms joined by shared electrons. Many have lower melting and boiling points than ionic compounds. Many do not conduct electricity because they do not have free moving ions or electrons.
Section 4Using properties
The thing to remember is that structure affects properties. If a question says a substance dissolves in water and conducts electricity as a solution, ionic compound is a strong clue.
Examples
Table salt is made from sodium ions and chloride ions. Is it ionic or covalent?
It is ionic because it is made from positive and negative ions in a fixed ratio.
A compound has a low boiling point and does not conduct electricity. Which type is it more likely to be?
It is more likely covalent. Many covalent compounds have lower boiling points and do not conduct electricity.
Now let's water it
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