Intermolecular forces- book

• Hydrogen bonding is a stronger force than dipole-dipole and dispersion forces.
• The kinetic molecular theory of gases explains that particles of gas are far apart from each other and are arranged randomly.
• A weak attractive force is present between a pair of gas molecules; hence, gases can fill up any container of any shape and size.
• Gas is also the most compressible of the three main states of matter.
• Gas has a high molecular velocity and the lowest density among the three states.
• The properties of gases differ from those of liquids and solids.
• Unlike in gases, the molecules of solids and liquids are nearer to each other.
• For liquids, the molecules are not freely moving and, thus, are bound by an intermolecular force of attraction.
• Liquids are only slightly compressible, have higher density than gases, and have a definite volume.
• Solids behave differently from liquids and gases because the molecules in solids are closely packed.
• Solids are held together by different intermolecular forces of attraction and electrostatic attraction.
• Solids cannot be compressed because the distance between their molecules is very small.
• The particles in solids cannot move freely from place to place; hence, they have a fixed shape and volume.
• Intermolecular forces of attraction are the attractive forces between neighboring particles (including molecules, atoms, and ions).
• These forces are milder and weaker than the bonds that hold chemical compounds together.
• Intermolecular forces arise from the electrostatic attraction between the positive charge of one particle and the negative charge of another nearby.
• Intermolecular forces can be Van der Waals forces, which are interactions between neutra molecules.
• Van der Waals forces are categorized into dipole-dipole interaction, dipole-induced dipole interaction, and dispersion forces.
• Other types of intermolecular forces also include ion-dipole, ion-induced dipole, and hydrogen bonding.
• A dipole refers to the formation of a positive pole and negative pole of a molecule.
• If a polar molecule approaches a nonpolar molecule, it attracts some electrons of the nonpolar molecule, causing these electrons to gather on one side of the molecule, forming a partially negative pole and a partially positive pole on the opposite side, known as an induced dipole.
• Dispersion forces arise when the electrons move in a direction away from one side of the molecule, resulting in an induced dipole within the molecule.
• The ion-dipole attraction exists between an ion and a polar molecule, where a positive ion attracts the partially negative side of a polar molecule, and a negative ion attracts a partially positive side.
• In these molecules, H is always positive since the adjacent atom attracts the electrons.
• The charge and size of the ion, the magnitude of the dipole, and the molecule size all determine the strength of the interaction.
• Dispersion forces, also known as London forces, exist in both polar and nonpolar molecules, and are most significant for nonpolar molecules.
• Dipole-dipole interaction is evident in polar molecules, which form when atoms share electrons unequally, making one atom partially negative (8 -) and the other partially positive (8 +).
• Hydrogen bonding is a special type of dipole-dipole interaction that exists between polar molecules that contain an H atom covalently bonded to highly electronegative atoms of fluorine (F), oxygen (O), and nitrogen (N).
• Dispersion forces become stronger when the number of atoms and the molecular mass increase, because the number of electrons also increases.
• Ions that approach a nonpolar molecule can induce a dipole in it, an interaction called ion-induced dipole.
• The induced dipole allows attraction of the molecule to another molecule.
• A dipole-dipole interaction exists when the positive pole of one polar molecule is attracted to the negative pole of another polar molecule.
• Hydrogen bonding happens when the positive H atom of one polar molecule interacts with the negative F, O, or N of another polar molecule.
• Huge ions and molecules exhibit low interaction because of the distance separating them.
• An interaction called dipole-induced dipole exists when a polar molecule forces an atom or a nonpolar molecule to become a dipole.
• A nonpolar molecule has an equal distribution of electrons throughout the molecule, thus it has neither a positive nor negative pole.
• For molecules with three or more atoms, both the bond polarity and the molecular geometry determine whether the molecules are polar or nonpolar.
• In case of water (HO) and methane (CH OH), the lone pairs of oxygen cause the bonding pairs to bend.
• Water (HO) and methane (CH OH) are polar molecules because the O and H,C

  O are polar bonds.
• Covalent or metallic if less than 0.5

  Polar Covalent if 0.5 to 2.0

  Ionic bond if greater than 2.0