If two hydrogen atoms can be positioned so that they can share electrons, both atoms will be 'satisfied'. The resulting molecule is a diatomic molecule of hydrogen, H 2. Covalent bonds can be indicated in a number of ways. One common method is to use electron dot diagrams. Pairs of dots between the symbols for two atoms indicate a bond between them.
Covalent bonds can also form between two atoms of different elements.
Carbon, with four electrons in its outermost L electron energy level, will seek to share in four covalent bonds. Complete the electron dot diagram of the methane molecule. Knowing the number of electrons present in an atom, and the number of those electrons available in the outermost energy ring, will allow you to determine how many covalent bonds a given atom can be engaged in. Hydrogen, oxygen, nitrogen, and oxygen are the four elements that are most common in living organisms. These are the elements that we will be most concerned with.