BONDINGChapter 6

CHEMICAL BONDINGChemical bond – mutual electrical attraction between the nuclei and valence electrons of different atoms that bind atoms together

IONIC BONDINGmetal (cation) + nonmetal (anion)

electrons are gained or lost

COVALENT BONDINGnonmetal + nonmetal electrons are SHAREDnonpolar – electrons are shared equally (examples: F2 and O3

polar – unequal sharing of electrons (examples: H2O and NH3)

molecule – covalent compound (a neutral group of atoms that are held together by covalent bonds)

chemical formula – number of atoms in a compound (example: water)

CHARACTERISTICS OF COVALENT BONDS

bond length – the distance between two bonded atoms

small bond length = strong bond

long bond length = weak bondbond energy = energy required to break a bond

high energy = strong bondlow energy = weak bond

LEWIS DOT STRUCTURESOctet rule – compounds are

formed so that each atom has eight electrons in its outer shell

EXCEPTIONS – hydrogen & helium Examples: N, H, F, F2 and NH3

unshared electrons are called lone pairs

single bond – sharing one pair of electrons between two atoms

double bond – sharing two pairs of electrons between two atoms (examples: O2 and C2H4)

triple bond – sharing three pairs of electrons between two atoms (examples N2 and C2H2)

RESONANCEMore than one correct Lewis dot structure

SO2

SO3

IONIC BONDING cations and anions form a neutral compound lattice energy – the energy released when

one mole of ionic crystalline is formed from gaseous ions

ionic bonds are stronger than covalent covalent compounds tend to have lower MP

and BP ionic compounds are hard and brittle

POLYATOMIC IONSnitrate = NO3

-

nitrite = NO2-

sulfate = SO4-2

sulfite = SO3-2

hydroxide = OH-

ammonium = NH4+

carbonate = CO3-2

bicarbonate = HCO3-

METALLIC BONDINGchemical attraction that results from the attraction of metal atoms and surrounding electrons

high electrical and thermal conductivity

malleability ductility

MOLECULAR GEOMETRY VSEPR theory – repulsions between the

sets of valence electrons around the atoms causes the sets to be as far apart as possible

SHAPES: Linear – only two atoms bonded (F2) or

central atom bonded to two other atoms with NO lone pairs (CO2)

Bent – central atom bonded to two other atoms and has lone pairs (water)

Trigonal planar – central atom bonded to 3 other atoms with NO lone pairs (SO3)

Trigonal pyramidal – central atom bonded to 3 other atoms and 1 lone pair (NH3)

Tetrahedral – central atom bonded to 4 other atoms with NO lone pairs (CH4)

BOND ANGLESlinear = 180o

bent = 120o (when there is 1 lone pair)

bent = 109o (when there are 2 lone pairs)

trigonal planar = 120o trigonal pyramidal = 109o tetrahedral = 109o

INTERMOLECULAR FORCESdipole-dipole – between two different

elements in the same compound (H-Cl)

hydrogen bonding – strong dipole forces between H and SONF (the strongest IMF) (water and ammonia)

London dispersion forces – between the same type of atom (O2) – also called van der Waals forces