The Periodic Table
The periodic table contains about a hundred or so elements that have been currently discovered. The rows are known as periods and elements of the same period have the same number of electron shells. The columns are known as groups and elements of the same group have the same number of electrons on their outer shell. Group one has one outer electron,
An element is a substance that cannot be broken down into anything simpler. KCl for example (potassium chloride) is NOT an element because it can be broken down into K (potassium) and Cl (chlorine). The potassium and chlorine are the elements.
A compound is two or more elements chemically bonded together. An example would be KCl (potassium chloride), which consists of the elements potassium and chloride chemically bonded together.
Atoms are the building blocks of substances.
Molecules are two or more atoms bonded together. It doesn’t have to be a compound. Elements such as O2 and Br2 are diatomic molecules – they exist in pairs.
