Could someone explain to me what the intermolecular forces are? There's Ion-dipole, H-bonding, dipole-dipole, ion-induced dipole, dipole-induced dipole, and dispersion. These are in order of strength. Could you also go into detail as to what an ion is and what a dipole is and examples for all of these? Preferably with pictures and words if that's possible?

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Intermolecular Forces are those forces of attraction that are present between two molecules. These are weaker forces.

Before moving into details, let's see what an ion and a dipole are.

Ion: It is an atom or a molecule with a charge. The charge may be positive or negative. When an atom loses electrons, they become positively charged ions, known as Cations and when an atom gain electron, they become negatively charged ions, known as Anions. For example :

  • Cations like Na^+, Ca^2+, Al^3+
  • Anions like F^-, O^2-, N^3-

Dipole: The word dipole, Di means two and Pole means end. So Dipole is pair of two equal and opposite charges separated by some distance. Dipole occurs when there is an electronegativity difference or there is unequal sharing of electrons between two atoms. For example HCl----HCl

Hence, an ion is formed by losing or gaining an electron, while a dipole is formed by the unequal sharing of electrons.

Depending upon the type of molecules, we have different types of Intermolecular forces present:

  1. Ion dipole: This type of interaction present between an ion and a dipole. Example when NaCl mixed in H2O. The interaction present between Na+ or Cl- and H2O is an Ion Dipole.
  2. Hydrogen bond: It occurs when the Hydrogen is bonded to strong electronegative atoms like Fluorine, Oxygen or Nitrogen. Example H2O: The H bond is present between H of one molecule and O of other molecule of H2O.
  3. Dipole-Dipole: This interaction present between polar molecules having permanent dipole. Example: between HCL molecules.
  4. Ion-Induced dipole: It occurs between Ion and non polar (no dipole) molecule. Due to the presence of an ion, the nearly placed non polar molecule may get a temporary dipole (induced dipole). Example Fe^2+ ion and O2 ( non polar molecule).
  5. Dipole-Induced dipole: It occurs between polar and non polar molecule. Due to presence of polar molecule, the nearly placed non polar molecule may get a temporary dipole (induced dipole). Examples: HCL, a polar molecule and Cl2, a non polar molecule.
  6. Dispersion: This type of interaction can be present between any type of molecule. Due to movement of electron in the molecules, charge separation may occur, which results in development of dispersion forces between molecules. Example: F2 molecules.
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