Two or more different elements held together in fixed proportions by attractive forces called chemical bonds. The compounds are substances created when multiple chemical elements are chemically held together. However, substances that consist of mixtures are not chemically attached to one another. The types of bonds that bond elements together in a compound are associated between two kinds of bonds called ionic and covalent. These elements in any substance are always in attendance within fixed ratios. It should also be noted that water has two hydrogen atoms and one oxygen atom.