A compound is a material made from two or more chemical elements that have bonded. The two main types of compound bonds are covalent bonds and ionic bounds.
In chemistry, atoms bond together to create different types of compounds by either sharing or transferring electrons from one element to another. When a bond is shared, it is a covalent bond. Transferred electrons occur in ionic bonds. It is also important to note the difference between a compound and a mixture. In a mixture, different substances mix together, but the atoms from each substance in a mixture do not bond together. Some substances only form a mixture when brought together, but others bond immediately. This process can happen gradually, such as when iron comes in contact with oxygen to form rust. At other times, a compound forms more quickly, such as when oxygen and lithium are mixed.
One classic example of a compound occurs with the elements of hydrogen and oxygen. These elements are both in gas form at room temperature. However, the compound that forms from them, water, exists in liquid form instead. This demonstrates how a compound of two elements is totally different than the elements that form the compound.