 A bond is an attraction that holds two particles together. In a water molecule there are two bonds. Each one joins one hydrogen atom to the central oxygen atom. It's because of chemical bonding that our universe contains more than just the hundred odd naturally occurring elements that we know to exist. Bonding turns elements into compounds and gives us the almost infinite variety of different substances that we encounter every day. All bonds form because of electrostatic attraction. Electrostatic attraction is the force that pulls two oppositely charged particles together. It is electrostatic attraction that keeps negatively charged electrons close to the positively charged nucleus of an atom. It's this attraction that must be broken when an atom loses an electron to become an ion. Electrostatic attraction can also occur between atoms. That is, between the electrons of one atom and the protons of another. This binds atoms together into macroscopic substances. There are three types of bonding to know about. We're going to go into them in detail in later videos, but here's a quick summary. There's ionic bonding. This occurs between oppositely charged ions, like between a sodium ion and a chloride ion in table salt. There's covalent bonding in which two atoms share electrons and the attraction is between the nuclei of the atoms and the shared electrons. This is the bonding that holds two hydrogen atoms together to form a hydrogen molecule. And there's metallic bonding where the attraction is between the nuclei of one atom and the electrons of many other atoms. This is the bonding you find in all the metals.