What is an element?
An element maybe defined as any substance that :
- Contains only one kind of atom.
- It cannot be broken down into a simpler form due to either a chemical or physical means (Copper or Sulphur)
- Can exist as either atoms or molecules (Oxygen or Nitrogen)
- Elements are arranged in the periodic table and are assigned a unique symbol based on their name.
- Elements are divided into three categories that have characteristic properties: metals, non metals and semi – metals.
What is a compound?
A compound consists of two or more elements bonded together through a chemical reaction. A compound can be separated into its constituting elements only through a chemical reaction.
Types of compounds
These are divided into ionic compounds and covalent compounds.
1. Ionic compounds
They are made of electrically charged atoms or molecules, as a result of gaining or losing electrons. Ions of opposite charges form ionic compounds and usually a metal reacting with a non – metal.
2. Covalent compounds
Also known as molecular compounds, these are formed when two non metals react with each other. The elements form a compound by sharing electrons, resulting in an electrically neutral molecule.
How do we write a compound formula?
The names of compounds are their chemical formula. These are generally descriptions of their composition and the valency of the elements. An element can form a compound with another element, only if the outer shell has electrons to either give or space to take electrons to form the electron octet.
The naming is done by :
- Writing the symbol for the composition of the compound with the cation first and the anion after.
- Determine the valance or charge of each element and place it in brackets above the symbol.
- Balance the total positive and total negative charge on the cation and anion. The total of cation and anion must be zero.
Most compounds are named by the elements’ position on the periodic table.