These are aluminum atoms. An atom is the smallest particle of an element that has the properties of that element. Each element has its own type of properties. Chemists use symbols to represent elements. A symbol is a letter or picture used to represent something.
Chemists use one or two lettters to represent elements.
The symbol for aluminum is Al. The symbol for oxygen is O. A model of an oxygen molecule . Oxygen stoms are joined in pairs. To write a pair of oxygen atoms using symbols, we use the symbol O and the number 2. The 2 is a subscript.