Nature of a Covalent Bond

In covalent bonding, the positively charged nucleus of each atom simultaneously (at the same time) attracts the negatively charged electrons that are being shared. The electrons spend most of their time between the atoms. The attraction between the nucleus and the shared electrons holds the atoms together.
The simplest kind of covalent bond is formed between two hydrogen atoms. Each hydrogen atom has 1 valence electron. By sharing their valence electrons, both hydrogen atoms till their outermost energy level. Remember, the outermost energy level of a hydrogen atom is complete With 2 electrons. The two atoms are now joined in a covalent bond.

Chemists represent the electron sharing that takes place in a covalent bond by an electron-dot diagram. In such a diagram, the chemical symbol for an element represents the nucleus and all the inner energy levels of the atom-that is, all the energy levels except the outermost energy level, which is the energy level with the valence electrons. Dots surrounding the symbol represent the valence electrons.
A hydrogen atom has only 1 valence electron.