The atoms in organic molecules are held together by what type of bonds?
Organic molecules contain by and large, electron-precise COVALENT bonds between carbon, hydrogen, oxygen, and nitrogen....in which electrons are shared between positively charged atomic nuclei.
Organic molecules are generally held together by intermolecular forces called van der Waals forces.
There are three types of van der Waals interactions.
The first one is the dipole-dipole one which is also called Keeson interaction. It exists between polar molecules (so molecules that have an electric charge). It is an electrostatic interaction and its intensity depends on the distance between the molecules and their partial charge. It is usually a strong interaction.
A particular type of dipole-dipole interaction is the hydrogen bond. It occurs when we have a hydrogen atom which is covalently bound to a small and very electronegative atom. When this happens, the small atom gains electrons from the hydrogen atom, so that it becomes slightly negatively charged. As a consequence, the hydrogen atom becomes slightly positively charged and it can bond with another electronegative atom.
This type of interaction is stronger than other dipole-dipole interactions but weaker than covalent or ionic bonding. An example of hydrogen bond in organic molecules is in DNA.
The second interaction is the Debye force, which is the permanent dipole-induced dipole. It occurs between polar and non-polar molecules. When we put an atom in an electric field, its cloud of electrons is distorted and attracted to the positive pole. The same thing happens to the positively charged nucleus, which becomes attracted to the negative pole. This process creates an induced dipole, which bonds with the permanent dipole.
The last interaction is the London force, between an induced dipole and an instantaneous dipole, so between non-polar molecules.
A non-polar atom can become polar just for one moment due to the movement of its electrons around the nucleus and this generates an instantaneous dipole. This type of dipole produces an electronic field which creates an induced dipole that is going to bond with the instantaneous one.