An atom of chlorine, on the other hand, with seven electrons in its outer shell would like to accept one electron. When it does, it will have one more electron than protons and become a negative ion with a -1 charge. When sodium and chlorine atoms are placed together, there is a transfer of electrons from the sodium to the chlorine atoms, resulting in a strong electrostatic attraction between the positive sodium ions and the negative chlorine ions. This explains the strong attraction between paired ions typical of the gas or liquid state. Formation of ionic bond in NaCl.
Some atoms like to share electrons to complete their outer shells.
Each pair of shared atoms is called a covalent bond. Covalent bonds are called directional because the atoms tend to remain in fixed positions with respect to each other. Covalent bonds are also very strong. Since the bonds are primarily covalent, the electrons are shared between the hydrogen and oxygen atoms. However, the electrons tend to spend more time around the oxygen atom.