Inorganic Flashcards
max oxidation states of G1, 2, and 13
+1, +2, +3
discrete E^n- and E^n+ ions exist only for metals and nonmetals of what ox #? specific
metals up to +3, and nonmetals having -ve ox #
what do elements of high +ve ox # exist as?
they do not exist as monatomic ions X^n+
as molecules (oxides, chlorides) in water as oxyacids, or corresponding polyatomic anions
minimum ox # of metals
0
minimum ox # noble gases
0
what is the ‘most stable state’?
generally the most naturally occurring one
it is the most RELUCTANT REACTANT in redox, ‘weak’.
oxidants and reductants in terms of ox #
elements in the MAX ox state can only act as an OXIDANT (accept e-)
elements in MIN ox state can only act as REDUCTANTS (e- donor)
intermediate states can act as both (like In+ or Tl+)
oxidant / reductant for states above and below most stable state
HIGHER Nox than most stable = good OXIDANT
LOWER Nox = good REDUCTANT
max ox number of s and p block elements
other than O and F,
Max Nox +z where z is the number of valence electrons
Nox lower than the max by 2 are common for p-block elements
min ox # for nonmetallic and metalloid elements
negative, = number of electrons needed to fill the valence shell.
eg. for P in G15, -3 minimim
trend in acidity of oxides across the periodic table
from basic oxides on the left (metals), to amphoteric oxides in the middle (eg. Al2O3) to acidic oxides at the right (non-metals)
metals are good _____
reductants - they are in their lowest oxidation state, 0
Good reductants
metals, H2
Boron position on periodic table
exists as what in molecules?
B is the top G13 element.
Metalloid (NOT a metal)
exists as B(III) in molecules B2O3, BCl3 (molecular)
difference in ionic and molecular chlorides reaction in water
Ionic chlorides dissolve
molecular chlorides REACT w/ H2O form hydroxides (eg. BeCl2 forms Be(OH)2 and HCl at pH7) and hydroxyanions (eg. Be(OH)4^2- in strong base)
describe G1, 2 and 13 oxides and hydroxides in aq solution
electropositive metals (G1, most of G2) exist as cation hydrates (eg. Li+(aq)) at ALL pH and have BASIC oxides.
Less electropositive metals Be, Al and Ga exist as
insoluble oxides/hydroxides at pH 7,
as cation hydrates in LOW pH by reacting w/ H+,
and as hydroxyanions at HIGH pH by reacting w/ OH-.
eg. Be2+(aq) in acid, Be(OH)2(s) at pH7, Be(OH)4^2- in base.
have AMPHOTERIC oxides
Boron non-metallic, doesn’t form discrete cation (exists as B(OH)3 in acid and pH7) exists as hydroxyanion in high pH.
ACIDIC oxide
how does the acidity of oxides of metallic elements vary with ox states?
Metals at LOW ox states (+1, +2) tend to have BASIC oxides
moderate (+3, some +2) AMPHOTERIC
very high (+4) acidic
In general, elements that form acidic oxides exist as ____ in aq soln
exist as ANIONS in aq soln, rather than hydrated cation
describe general acidity of G1,2,13 halides in H2O
G1 and most G2 are ionic solids (hence water soluble to give hydrated ions)
not acidic
Be, Al, Ga, In chlorides predominantly ionic, dissolve to give hydrated ions
WEAK ACID
BCl3 is covalent, gas
dissolves in H2O –> B(OH)3 + HCl
ACIDIC
acidity of cation hydrates of ions with high charge density
WEAK acids (Be, Al, Ga, In)
acidity of the oxide anion
STRONG BASE
small anion, high charge
so metal oxides basic because O2- reacts and changes the pH
why are G1 oxides basic
due to ionic character and the basic O2- ion
solubility of G2 hydroxides
slightly water soluble Ca(OH)2 == Ca2+ + 2OH- in high pH, add OH-, Ca(OH)2 ppt add H3O+, Ca(OH)2 decrease hence basic as it reacts w/ acid
non metals in G14
Carbon
Metalloids in G14
Si, Ge
Metals in G14
Sn, Pb
acidity of G14 oxides
nonmetal oxides: acidic gas like CO2, or neither acid/base like CO
Metalloid oxides: acidic solid, GeO amphoteric solid
Metal oxides: amphoteric solids
amphoteric oxides products in acids and bases
in acid, add H+, form cation and water
base, add OH-, form hydroxyanion
Are G14 chlorides in the highest oxidation state ionic or molecular?
E(IV) chlorides are all MOLECULAR, all liquid
ECl4
most stable states of G14 elements
all +4, except Pb is +2
so all except Pb, +4 is a weak oxidant (Pb(+4) strong oxidant)
possible oxidation states of G14 elements
+4, +2 and 0
C also has -4, in CH4
oxides of G15 elements acidity
+5 oxides are ALL ACIDIC
+3 oxides:
nonmetals = acidic
metalloids = amphoteric
metals = basic
nonmetals in G15
N, P
metalloids in G15
As, Sb
metals in G15
Bi
what is formed when G15 oxides react with excess water?
oxoacids
eg. N2O5 —> HNO3
N2O3 —–> HNO2
what is produced when G15 oxoacids react with OH-?
anions
eg. HNO3 —-> NO3 -
HNO2 —> NO2 -
possible oxidation states of G15 elements
+5, +3, 0, -3
for N: +5, +4, +3, +2, 0, -3
max ox state of O and F
0
therefore can only act as an oxidant
most stable state for G15 elements
N = 0 P = +5 As = +5, +3 Sb = +5, +3 Bi = +3
general rule for most stable state for G1, 2, 13-16 elements
Except O and F,
most stable = maximum ox number
for heavier period 5 metals Tl, Pb, Bi, most stable is
max-2
what type of particle exists as oxoacids?
very small non-metal cations
oxoacids or their anions are the predominant form in aqueous solution for the non-metals in positive oxidation states.
eg. C, N, P, S, Cl as (HO)nE=O
(HO)2CO or H2CO3
hydroxoacids general formula
E(OH)n
do not donate H+, they accept OH-
eg. B(OH)3 + OH- —> B(OH4)-
charge density formula
Z^2/r
Z = charge, r=radius
trend in charge density across P3 ions
cations: charge density INCREASES as charge increases and radius decreases
anions: charge density DECREASES, as charge decrease outweighs radius decrease
Al3+ and P3- are the ions with the highest charge density
hydrated ANIONS of high charge density - what happens?
water molecules cleave, forming OH- and the conjugate acid of the anion.
[(OH2)5X…H-OH]^n- –> (OH)5XH^(+1-n) + OH-
How do G14, 15, 16, 17 anions exist in water?
Anionic conj acids (C4-, N3-, O2-… etc) accept further protons until charge density is low enough to exist in water.
G14: CH4 G15: N3-, P3- ------> EH3 these are fully protonated G16: O2-, S2- -----> EH- exists as EH- in H2O. G17 exists as X-, charge density is low enough
which group anions are?? strong bases?
G14 - 16 anions and H-
how does the charge density of a cation affect the acidity of its hydrate?
higher charge density of cation, the more acidic the hydrate, until the major species in solution are hydroxoacids and oxoacids.
acidity and basicity of HnX trend
higher going across and down the periodic table
CH4, NH3, H2O weak acids
H2S, HF amphoteric
HCl, HBr, HI strong acids
basicity trends opposite - basicity decreases across and down.
C4-, N3-, O2- strong bases
F- neither
Cl-, Br-, I- weak bases
Xn- ion acidity
except halide ions, Xn- are STRONG BASES
exist in aq form as a mixture of protonated form and OH-.
how does bonding relate to basicity of a polyatomic anion?
the strongest base anion has the highest charge density at the oxygen.
more O’s, the more the charge is delocalised (hence oxoacids have many O groups)
oxidation states of G16 elements
-2, 0, +4, +6
except O: -2, -1, 0.
Oxygen can only act as an oxidant because
it has no positive oxidation states.
most stable states for G16
O: -2 S: -2, +6 Se: +4, +6 Te: +4 E(IV) becomes more stable going down the group
elements act as an oxidant towards elements on the Left or Right?
on the LEFT
S acts as an oxidant toward Ca, but not F (F accepts e- from S)
when can H2SO4 act as an oxidant?
despite being most stable state, H2SO4 can act as an oxidant in STRONGLY ACIDIC CONDITIONS (absence of H2O)
product could be SO2 (4+), S (0), H2S (-2)
possible oxidation states of G17 elements
-1, 0, +1, +5, +7
EXCEPT F, only -1 and 0
Cl also has +3 (all odd numbers and 0)
all halogens can act as ____
oxidants
all halides can be ____
reductants
despite being the most stable state for all
all elements/compounds containing a halogen in a positive oxidation state are
OXIDANTS
relative oxidant and reductant strength of halogens and halides
Oxidants from very strong to moderate:
F2, Cl2, (conc H2SO4) Br2, I2
Reductants from very WEAK to moderate:
F-, Cl-, Br-, I-
when do displacement reactions for halogens/halides occur?
only when the reactant halogen is a stronger oxidant than the product halogen, and the reactant halide is a stronger reductant than the product halide.
eg. Br2 + 2I- –> 2Br- + I2
H2SO4 conc can oxidise which halides?
conc H2SO4 oxidant strength between Cl2 and Br2
so it can oxidise Br- and I-
product SO2 stronger reductant (I-) will give a more reduced product (S or H2S)
Oxidation states of Nitrogen
-3, -2, -1, 0, 1, 2, 3, 4, 5
