1. Electron Sharing . . . aww isn’t that nice
Covalent Bonding
Electron Sharing aww isn’t that nice

2. Overview
The general rule of thumb is that 2 non-metals make an covalent bonds. Neither is satisfied “giving up” its electrons entirely but sharing is perfectly fine. Their pre-school teachers would be proud! 

3. Overview
Electrons have a negative charge and the nuclei they surround have a positive charge. When the two particles approach one another the electron paths can overlap.
When this happens, under certain circumstances, the electrons that are between two nuclei can be attracted to both nuclei, holding them together.

4. Covalent Bonding
This force of attraction is known as a chemical bond. When the atoms form a bond they become lower in energy and the system is more stable.
The energy saved by moving to a more stable situation is released as heat. For this reason bond formation is always exothermic, i.e. heat energy is released.

5. Covalent Bonding
Conversely, in order to break a chemical bond energy must be used - it is an endothermic process.
Covalent bonding occurs between atoms of non-metals

7. # of covalent bonds formed
Covalent Bonding
Atoms form covalent bonds for reasons very similar to why other atoms for ionic bonds; they are most energetically satisfied with 8 electrons  a stable octet.
The difference lies with the electronegativity values, atoms that form covalent bonds do don’t easily give up their electrons to make ionic compounds.
Atoms will typically form the same number of covalent bonds as they have unpaired electrons.
Group # 2 13 14 15 16 17
# of covalent bonds formed 2 3 4 1

8. H H The Mechanics A covalent bond is formed between each H atom .
Both are satisfied because they have filled their energy level (ie attained noble gas configuration).
Once we say that a bond has “formed” we replace the two single electrons involved with a solid line between the two atoms.

9. Electron sharing
To form a single covalent bond one electron is provided by each of the bonding atoms making a shared pair. The simplest situation occurs when two atoms of a non-metal share one pair of electrons.
Chlorine molecule formed by two atoms sharing one pair of electrons. Here, we can see that although originally each chlorine atom has only seven electrons in its outer shell, after bonding it has eight (an octet), making the molecule more stable than the sum of the original atoms.

10. Diatomics (HOBrFINClSP) and More
These 9 elements do not exist as single atoms in their elemental form.
H2, N2, O2, F2, Cl2, Br2, and I2 are what we call diatomics.
Phosphorus exists as a tetrahedron, with the atoms at the vertices, P4.
Sulfur exists as an 8-membered ring, S8.
In each case, we say there is a single bond between each atom.
There is a bond order of 1 (BO = 1) between each atom.

11. Multiple Bonding
Nitrogen and Oxygen have multiple unpaired electrons so in order to attain noble gas configuration they each need to share multiple times.
Oxygen needs to form 2 covalent bonds while nitrogen forms 3.
Triple bond, bond order of 3. The N2 triple bond is among the shortest and strongest bonds known.
Double bond, bond order of 2. The O2 double bond is much shorter than a single bond.
As the bond order increases, the distance between the two atoms decreases.
Overall a multiple bond has more potential energy stored in it than a single bond. We must be careful though not to assume that simply because the atoms are closer that the bond is necessarily stronger.