G15 Flashcards
give brief overview of G15
lower OS more stable down group
nearly all G15 elements involve covalently bonded compounds
N is a gas, P is covalent solid, As and antimony are metalloid semiconductors and Bismuth is a metal
describe bonding of nitrogen
N is very stable diatomic gas with triple bonds which has high dissociation energy and kinetically inert due to lack of dipole moment
N-N single bonds are weak due to lone pair - lone pair repulsions
what are the three main allotropes of phosphorus
white black and red
white: P4 standard state for P as all other allotropes convert to this when melted at 1atm
white: p-p-p angle 60
p-p distance 2.21 angstrom
sp3 p atoms
Very reactive due to bond strain preferred sp3 angle and readily accessible LP
Black: most thermodynamically stable least reactive form of P
obtained by heating white P under pressure
describe red phosphorus
describe process of matches
found in several crystalline forms, it is of intermediate reactivity and used in matches.
1 red P, heat from friction 2 vaporises as white P4 3 spontaneously ignites 4 KClO3 n match decomposes 5 O2 generated 6 S on match ignites 7 Fire
how are As Sb and Bi structured and how do they react with oxygen
Greys solids under standard conditions
lattice structure resembling that of block phosphorus
all combine readily with O2
4M + 3O2 -> 2M2O3
with heat
what are the production and uses of N2
obtained by fractional distillation of liquid air used to make ammonia in bosch-Haber process
gas used to provide unreactive atmosphere
liquid used as refrigerant
used to inflate air bags by rapidly producing NaN3
how is phosphorus extracted and used
extracted from phosphate rock
2Ca3(PO4)2 + 6SiO2 + 10C -> P4 + 6CaSiO3 + 10CO
used for production of fertilisers and animal food supplements
converted to H3PO4
PCl3 industry applications, precursor to many organophosphorus compounds eg flame retardants and insecticides
how are G15 compounds structured
whats special about N compounds
Covalent compounds OS of +3 or +5
N(V) compounds only possible in compounds containing multiple bonds
Small in size so cant form covalent bonds to more than four atoms
going down group +3 OS more stable but this trend less defined than for G13 and 14 elements
explain the lewis basicity on R3E compounds
E = G15
R3E (E=G15) all lewis bases due to LP
Ability for it to donate e depends on electronegativity of the R group, higher electronegativity lower lewis basicity
G15 element and also steric effects influence it
explain lewis acidity of ER3 compounds
can be lewis acids because presence of low energy empty valance d orbitals. .
PX3 + X- –> PX4-
R3N has no low-lying empty orbitals for accepting e
more electronegative R the higher the lewis acidity
ER5 cant be bases no LP, act as acids as vacant orbitals,
PF6- formed from PF5 with F-
describe reactivity fo trihydrides MH3
get more reactive and less thermodynamically stable down group
NH3 is stable in presence of oxygen while PH3 reacts readily
PH3+O2 –> H3PO4
weak P-H bond due to orbital size mismatch
BP of hydrides varies irregularly down group
NH3»PH3
how is ammonia produced
used in agriculture as fertiliser and used a source of nitrogen
N2 + 3H2 2NH3
720 k
20260 pa
Fe2O3 catalyst
describe G15 halides
all G15 form trihalides those P downwards form pentahalides EX5
Trihalides with N all extremely unstable
2NX3 –> N2 + 3X2
large E(NtriplebondN) is driving force
down group halides more ionic and increasingly adopt infinite structures in preference to molecular ones
describe P halides
P trihalides are all stable
prepared by direct reaction of P with halogen
PF3 prepared via halogen exchange
2P + 3X2 –> 2PX3
PX3 + 3F- –> PF3 + X-
PX5 species on ionic/covalent borderline
PCl5 exist as isolated molecules in gas and liquid state, when solid exists as PCl6- PCl4+
what are the different nitrogen oxides
+1 nitrous oxide
N- = N+ = O NtbndN+ - O-
+2 nitric oxide free radical
*N=O dimer at low temps
+3 dinitrogen trioxide
+4 nitrogen dioxide and dinitrogen tetra oxide
+5 dinitrogen pentoxide. nitronium ion nitrate ion
