inter and intra forces

• Intermolecular Forces


  The relative strengths of intramolecular bonding (covalent bonding) and intermolecular forces (dispersion forces, dipole-dipole attraction and hydrogen bonding)
• Physical properties of molecular substances


  • Melting points and boiling points and non-conduction of electricity with reference to their structure and bonding
• Intramolecular bonds


  The strong bonds between the carbon and oxygen atoms within carbon dioxide molecules
• Intermolecular bonds


  The weak bonds between carbon dioxide molecules
• Weak intermolecular bonds


  The bonds that are broken when molecular substances such as water boil or melt, allowing the molecules to separate from each other while the atoms within the molecules remain bound to one another
• Dispersion forces


  The weakest of the intermolecular forces that exist between all types of molecules, as electrons are constantly moving
• Instantaneous dipole


  A dipole moment created when electrons spontaneously move to the far left or right of an atom, with the left-hand side having a partial negative charge and the right-hand side having a partial positive charge
• Dipole-dipole forces


  Forces that occur when the partially positively charged part of a molecule interacts with the partially negatively charged part of the neighboring molecule
• Hydrogen bonding


  A relatively strong force of attraction between molecules, where a hydrogen atom that is covalently bonded to either an oxygen, nitrogen, or fluorine atom within the molecule interacts with a lone pair of electrons on another molecule
• Molecules that do not contain hydrogen bonding


  • Molecules that have H-NOF atoms present, but hydrogen is not covalently bonded to N-O-F atoms within the molecule
• Intermolecular forces summary


  • Dispersion force
  • Dipole-dipole bond
  • Hydrogen bond
• Dispersion force


  Weak, but increases as the size of the atom or molecule increases
• Dipole-dipole bond


  Generally stronger than dispersion force but weaker than hydrogen bond
• Hydrogen bond


  Strongest intermolecular force but a lot weaker than a covalent bond
• The properties of molecular substances are determined by their intermolecular forces
• Intermolecular forces are responsible for a number of different physical properties including melting point, boiling point and hardness
• The strength of intermolecular forces reflects the amount of energy it takes to break the bonds between molecules
• At each phase of matter, solid, liquid and gas, molecules have a certain amount of kinetic energy that allows them to move around and overcome the forces that are maintaining the substance in a particular state
• Hydrogen bonds


  The strongest intermolecular forces, requiring more energy to break apart than permanent dipole-dipole forces, which in turn require more energy to break apart than dispersion forces
• Dispersion forces


  • The strength of dispersion forces increases as the size of the molecule increases, with larger molecules having higher melting and boiling points
• Dispersion forces


  • Molecules that form long chains tend to have stronger dispersion forces, compared to compact molecules with similar number of electrons, due to having more contact area to interact with neighboring molecules
• Dipole-dipole forces


  • The strength of the dipole-dipole forces is directly related to the melting and boiling points, with stronger dipole-dipole forces resulting in higher melting and boiling points
• Hydrogen bonding


  • Hydrogen bonding is 10 times stronger than a dipole-dipole bond but one-tenth the strength of an ionic or covalent bond, resulting in higher melting and boiling points