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Chemical Bonding

Definitions

electronegativity - the tendency of atoms in a molecule to attract a shared pair of electrons

intermolecular bonds - the bonds between molecules

valence electrons - the electrons in the outermost energy level of an atom

covalent bond - a sharing of atleast one pair of electrons by two non-metal atoms

bond energy - energy required to completely seperate two covalently bonded atoms

bond length - distance between the nuclei of two covalently bonded atoms

pure covalent (non-polar) - equal sharing of electrons

polar covalent - unequal sharing causing dipole

dipole moment - measure of the polarity of a bond

dative covalent - A dative covalent bond is a bond that is formed by the overlapping of orbitals and the sharing of an electron pair both of which belong to one atom

Dative Covalent Bonds

  • a molecule with a positive ion (needs electron) bonds to a molecule with a loan pair (donor atom).

  • overall charge becomes +.

Shape of Molecules

  • determined using VSEPR

Linear

  • bond angle 180

Angular

  • formed op 2 lone pairs

  • angle between bonded pairs - 104,5

Trigonal Planar

  • 120

  • no lone pair

Trigonal Pyramidal

  • 107,5 between bonded

  • single loan pair

Tetrahedral

  • 109,5 between bonded

  • no lone pairs

Trigonal Bipyramidal

  • 120 horizontally, 90 vertically

Octahedral

  • 90 all round

Polar Molecules

  • greater charge = more electronegative

  • size of atom - electrons closer to nuclei meaning stronger forces

non-polar bonds

  • no electronegativity dif

polar bonds

  • difference in electrongeativty pulls electron cloud one way = polar

If covalent

if the substance is ionic (nm → m), then becomes ionic with covalent characters at 1,7

  • if a molecule has polar bonds but is symetrical, the vector force equates to 0 and is therefore not a dipole (non-polar)