shapes of molecules and intermolecular forces

Question 1

electronegativity

Answer 1

ability of an atom to attract the electrons in a covalent bond

Question 2

non-polar bonds

Answer 2

• in non-polar bonds, the bonded pair is shared equally between the bonded atoms. A bond will be non-polar when:
• bonded atoms are the same
  -bonded atoms have the same or similar electronegativity

Question 3

dipole

Answer 3

separation of opposite charges

Question 4

permanent dipole

Answer 4

dipole that occurs in a POLAR covalent bond
- small charge difference across a bond that results from a difference in the electronegativities of the bonded atoms

Question 5

polar molecule

Answer 5

covalent bond or molecule where the electron density is shifted more towards one end than the other
- molecule will ONLY be polar if dipoles dont cancel out, so molecule must be asymmetrical

Question 6

induced dipole-dipole interactions

Answer 6

• instantaneous dipole is set up within an atom, due to electron density fluctuation
• this induces a diploe on a neighbouring molecule
• the induced dipole induces further dipoles on neighbouring molecules, which then attract one another
• forms induced dipole- dipole interactions or London forces
• these are only temporary as in the next instant of time the induced dipoles disappear

Question 7

strength pf induced dipole- dipole interactions

Answer 7

the more electrons in each molecule:
- the larger the instantaneous and induced dipoles
- the greater the induced dipole-dipole interactions
- the stronger the attractive forces between molecules

Question 8

anomalous properties of water

Answer 8

• hydrogen bonds extend outwards holding water molecules slightly apart and forming an open tetrahedral lattice full of holes. This causes liquid water to be denser than solid ice, as when ice melts the lattice collapses and the molecules move closer together. The bond angle around the hydrogen atom in ice is close to 180
• relatively high melting ang boiling point. Hydrogen bonds require high amount of energy to break, so has higher melting and boiling point then would be expected from just London forces