Ionic, Covalent, and Hydrogen Bonds

Ionic and Covalent Bonds are two different types of bonds that are seen in molecules. Both involve electrons. Atoms are able to achieve stability in their valence electrons through the interaction with other atoms. But how they do this can differ.

In the case of an ionic bond, an electron is simply transferred to another atom. By doing so, each atom is able to have a stable valence shell. It is called an ionic bond because the atoms become ions, a charged atom that has either lost an electron (negative charge) or has extra electrons (positive charge). Below is an animation of ionic bonding:

In this diagram, an electron from the sodium is transferred over to the chlorine atom. This enables the sodium atom to be stable, as it doesn’t have any electrons in its valence shell, and the chlorine is stable as well, as it has a full valence shell.

Covalent bonds are a bit different. Rather than transferring an electron over to another atom, the atoms “share” the electron.

In this case, the two chlorine atoms share an electron, enabling them to both achieve a stable valence shell. Sometimes, there is an unequal sharing of the electrons. This is known as Polar Covalent bonds. One note about covalent bonds – they can only occur when two electrons are shared by non-metallic atoms.

Hydrogen bonds exist between two polar molecules that contain hydrogen. Polar molecules have partially positive and negative ends. In hydrogen bonds, the partially positive end of one polar molecule is attracted to the partially negative end of another polar molecule. This is seen below:

As seen within this animation, the molecules, which in this case appear to be water, have both partially positive and negative ends. The hydrogen atoms are partially positive, whereas the oxygen atoms are partially negative. When water molecules are close to each other, the partially positive hydrogen ends find themselves attracted to the partially negative oxygen ends. This is a hydrogen bond.

http://www.accessexcellence.org/RC/VL/GG/cov_IonicBs.html provides another graphic that differentiates the ionic and covalent bonds.

http://www.elmhurst.edu/~chm/vchembook/161Ahydrogenbond.html provides more information on hydrogen bonds.

*All animations were taken from http://ithacasciencezone.com/chemzone/lessons/03bonding/mleebonding/