chemical bonding notes

traits of transition metals

have variable valencies, coloured compounds, used as catalysts

exceptions to octet rule

transition metals can have more or less than 8 electrons in its outer shell, elements near He usually have 2 electrons in outer shell

cation

positively charged ion

anions

negatively charged ion

complex ions one negative charge

hydroxide ion (OH-), nitrate ion (NO3-), hydrogencarbonate ion (HCO3-), permanganate ion (MnO4-)

complex ions two negative charges

carbonate ion (CO3-2), chromate ion (CrO4-2), dichromate ion (CrO7-2), sulfate ion (SO4-2), sulfite ion (SO3-2), thiosulfate ion (S2O3-2)

complex ions three negative charges

phosphate ion PO4-3

complex ions one positive charge

ammonium ion (NH4+)

intramolecular

between atoms - ionic, covalent bonding

intermolecular

within a molecule - van der waals, dipole dipole. hydrogen bonding

ionic bonding

the transfer of electrons

covalent bonding

sharing electrons usually between a metal and non metal

the diatomic elements

hydrogen H2, nitrogen N2, fluorine F2, oxygen O2, iodine I2, chlorine Cl2, bromine Br2

sigma bonding

head overlap of s orbital, sphere

pi bonding

sideways overlap of p orbital, dumbbell

single bonds made of

one sigma bond

double bonds made of

one sigma and one pi bond

triple bonds made of

one sigma and 2 pi bonds

tetrahedral

4 bonds, 0 lone, 109.5

pyramidal

3 bonds, 1 lone, 107

trigonal planar

3 bond, 0 lone 120

v-shaped

2 bond, 2 lone 104.5 (H2O) 102 ( H2S)

linear

2 bond, 0 lone, 180

explain the differnce in bond angles between H20 and H2S

lone pairs repel more than bonding pairs H2O has 2 lone and 2 bond pairs, this reduces the bond angle by 2.5

electronegativity

relative attraction for a shared pair of electrons in a single covalent bond (pulling power)

non polar

equal distribution of charge between the two atoms in the bond

polar

unequal distribution of charge

test for polarity

a charged rod brought towards a thin stream of liquid from a burette, if polar the stream will be attracted and bends towards rod.

how are polar covalent bonds non polar

symmetry the centers of positive charge and negative charge align and cancel each other

van der waals

non-polar, weak temporary bonds, low melting/boiling point, strength increases with size of molecular mass, exception 02 boiling point higher than H2 because molecule is bigger

dipole dipole

polar, stronger permanent dipoles, positive dalta attracts minus dalta, higher melting and boiling point

hydrogen bonding

special type of dipole dipole, H is bonded to more electronegative elements, F, N, or O. strongest, exception H2S has lower melting point than water even though its molecule is bigger as the effect of polarity is not as great as it is in water

solubility

like dissolve in like, same polarities will be soluble (there are attractive forces), different polarities will not be soluble, e.g. water, cyclohexane

measure the melting point

place the sample of crystals in the melting point capillary tube in the aluminium melting point block. heat the sample slowly using a hotplate. record the temperature whne metling occurs using a thermometer.

pure substance

has a fixed melting point only melts over a very narrow temperature range

impure substance

melts over a wider range of temperatures and at a lower temperature than the pure substance. /