The standard form periodic table lists 118 or so elements, how come you then find more substances around you? Simple: ability of atoms to react with one another to form new substances called compounds. When two or more atoms join or bond together, the resulting compound is unique (different chemical and physical properties).
Let's restate what bonding is about: The arrangement of electrons in the outermost shell of an atom determines how the atoms can bond to other atoms and form new molecules with different properties. Bonds are formed between atoms when electrons are transferred or shared between them.
Before you delve deep into chemical bonds, it is important to note the Octet Rule. The rule states that atoms should have either eight or multiple of eight electrons in the outermost shell or the highest energy shell. Why?