Intermolecular vs. Intramolecular Forces
Topics Covered: intermolecular forces, intramolecular forces, ionic bonding, covalent bonding, metallic bonding
When you hear the terms intermolecular and intramolecular forces, they sound very similar… You know that these are the forces that have to do something with the molecules, but one is “inter” and the other is “intra,” so what’s the difference? In this post, we’re going to distinguish the difference between two major forces that operate in a molecule, intramolecular and intermolecular forces.
Intermolecular forces are forces that exist between the molecules. There are three types of them, —London-dispersion forces, dipole-dipole attraction, and hydrogen bonding— and we covered all of them in depth in our other post, so make sure to check that out if you are confused!
Today, we’ll talk more in depth about intramolecular forces. Intramolecular forces, as the name implies, are forces that exist within the molecule. They are deeply associated with chemical bonding, when atoms bond together to form molecules or formula units. Like intermolecular forces, there are also three types of intramolecular forces: ionic, covalent, and metallic bonds.
An ionic bond is a bond that occurs when atoms completely transfer valence electrons from one to the other. In ionic bonds, the metal atom loses electrons to become a positively charged cation, and the nonmetal atom gains electrons to become a negatively charged anion (remember it as a negative ion). Remember, since an atom is losing electrons (which is negative), the atom becomes more positive. Then, since opposite charges attract each other, positive cation and negative anion will be attracted to each other to form bonds.
A covalent bond is a bond that occurs when nonmetal atoms share electrons. Depending on how electrons are distributed, the bond can be polar (distributed unequally) or nonpolar (equally). But don’t worry, we’ll get in depth about polarity in a later post!
Finally, metallic bonds are bonds that occur between metal ions. Positively charged atoms of the metal are in a lattice structure, and delocalized electrons, known as the “sea of electrons,” freely move around the metal ions. Because these electrons freely move around metal ions, they account for many physical properties of metal, such as being malleable, ductile, and good conductors!
Now, to summarize the difference, intermolecular forces are forces that exist between the molecules, while intramolecular forces are forces that exist within the molecules. Finally, I’ll end this post with an example. If you look at a water molecule, (H2O), intramolecular force exists between hydrogen and oxygen atoms, as they are bonded in polar covalent bonds. But between the water molecules, there exists a hydrogen bonding, a type of intermolecular force that makes water molecules attracted to each other!
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