DM - Inorganic chemistry and the periodic table *01 Flashcards

1
Q

where are transition metals found in the periodic table?

A

d-Block

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2
Q

what is a transition metal?

A

a d-Block element that can form at least one stable ion with an incomplete d sub-shell

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3
Q

why isn’t scandium a transition metal?

A

only forms one ion Sc3+

this has an empty d sub-shell

electronic config. [Ar]3d14s2 so when it loses 3 e- has electronic config. [Ar]

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4
Q

why isn’t zinc a transition metal?

A

only forms one ion, Zn2+

this has a full d sub-shell

electron config. = [Ar]3d104s2

when it form Zn2+ it loses 2 e- (both form 4s sub-shell) so it keeps its full 3d sub-shell

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5
Q

which sub-shell to transition metals lose electrons from 1st to form ions?

A

4s sub-shell

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6
Q

transition metals - special chemical properties

A
  1. variable oxidation states

2. form coloured ions in solution

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7
Q

transition metals - iron properties

A

oxidation states =
+2 and +3

coloured precipitate =
Fe2+ - green
Fe3+ - orange

coloured aq =
Fe2+ - green
Fe3+ - yellow

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8
Q

transition metals - copper properties

A

oxidation states =
+1 and +2

coloured precipitate =
Cu2+ - pale blue

colour in aq =
Cu2+ - blue

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9
Q

what is a complex ion?

A

a complex (or complex ion) is a central metal atom or ion surrounded by coordinately bonded ligands

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10
Q

what is a ligand?

A

an atom, ion or molecule that donates a pair of electrons to a central transition metal ion to form a coordinate (dative) bond.

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11
Q

what is ligand substitution?

A

one ligand can be swapped for another - usually causes a colour change.

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12
Q

how do ligands form bonds?

A

using lone pairs of electrons

they donate a pair of electrons to a central transition metal ion to form a coordinate (dative) bond

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13
Q

what is a mono/unidentate ligand?

A

ligands with one lone pair of electrons

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14
Q

what is a bidentate ligand?

A

ligands with two lone pairs of electrons

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15
Q

what is a polydentate ligand?

A

ligands with more than two lone pairs of electrons

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16
Q

ligand substitution reactions - what happens when ligands similar size?

A

the coordination number does change and neither does the shape

colour does change

eg. H2O, NH3 or CN-

for example
[Cr9(H2O)6]3+ + 6NH3 [Cr(NH3)6]3+ + 6H2O
octrahedral octrahedral
dark green purple

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17
Q

ligand substitution reactions - what happens when ligands different sizes?

A

change in coordination number and shape and colour

eg. H2O and Cl-

for example:
[Cu9H2O)6]2+ + 4Cl- [CuCl4]2- + 6H2O
octrahedral pale blue —-> tetrahedral yellow

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18
Q

ligands substitution reactions - why + what happens when substitution only partial?

A

happens when you add excess ammonia

for example:
[Cu(H2O)6]2+ + 4NH3 [Cu(NH3)4(H2O)2]2+ + 4H2O
octrahedreal in excess octrahedral
pale blue dark blue

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19
Q

what happens to transitions metals when react with sodium hydroxide?

A

form brightly coloured precipitates

copper 2+ does this with - NH3 - too

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20
Q

transition metal hydroxides + OH-: COPPER (II)

A

[Cu(H2O)6]2+ (aq) + 2OH- (aq) ——> [Cu(OH)2(H2O)4] (s) + 2H2O (l)
PALE BLUE percipitate
or
Cu2+ (aq) + 2OH- (aq) —-> Cu(OH)2 (s)

21
Q

transition metal hydroxides + NH3: COPPER (II)

A

[Cu(H2O)6]2+ (aq) + 2NH3 (aq) ——> [Cu(OH)2(H2O)4] (s) + 2NH4+ (aq)
PALE BLUE solution ——> BLUE precipitate

22
Q

transition metal hydroxides + NH3 (IN EXCESS!!) : COPPER (II)

A
  1. [Cu(H2O)6]2+ (aq) + 2NH3 (aq) ——> [Cu(OH)2(H2O)4] (s) + 2NH4+ (aq)
    PALE BLUE solution BLUE percipitate
  2. reacts further
    —> [Cu(NH3)4(H2O)4] (aq)
    DARK BLUE solution
23
Q

transition metal hydroxides + OH-: IRON (II)

A

[Fe(H2O)6]2+ (aq) + 2OH- (aq) ——> [Fe(OH)2(H2O)4] (s) + 2H2O (l)
PALE GREEN solution ——> DARK GREEN precipitate

when left standing
—-> green precipitate darkens

24
Q

transition metal hydroxides: what happens when [Fe(OH)2(H2O)4] (s) is left standing

A

green precipitate DARKENS

25
Q

transition metal hydroxides + NH3: IRON (II)

A

[Fe(H2O)6]2+ (aq) + 2NH3 (aq) ——> [Fe(OH)2(H2O)4] (s) + 2NH4+ (aq)
PALE GREEN solution DARK GREEN precipitate

when left standing
—-> green precipitate darkens

26
Q

transition metal hydroxides + OH-: IRON (III)

A

[Fe(H2O)6]3+ (aq) + 3OH- (aq) ——> [Fe(OH)3(H2O)3] (s) + 3H2O (l)
YELLOW solution —–> ORANGE precipitate

when left standing
—-> orange precipitate darkens

27
Q

transition metal hydroxides: what happens when [Fe(OH)3(H2O)3] (s) is left standing

A

orange precipitate DARKENS

28
Q

transition metal hydroxides + NH3: IRON (III)

A

[Fe(H2O)6]3+ (aq) + 3NH3 (aq) ——> [Fe(OH)3(H2O)3] (s) + 3NH4+ (aq)
YELLOW solution ——-> ORANGE precipitate

when left standing
—-> orange precipitate darkens

29
Q

can copper (II) hydroxide form complexes with ammonia (NH3)?

A

yes

30
Q

can iron (II) hydroxide form complexes with ammonia (NH3)?

A

no

31
Q

can iron (III) hydroxide form complexes with ammonia (NH3)?

A

no

32
Q

origin of colour in transition metals?

A

normally 3d orbitals of transition metals ions all have the same energy

when ligands bond to the ions they SPLIT the 3d orbitals, and some of the orbitals gain energy

this splits the 3d orbitals into two different energy levels

electrons tend to occupy the lower orbitals - to jump to higher orbitals they need the energy EQUAL to the ENERGY GAP
- they get this energy from visible light

33
Q

what is the amount of energy needed to make electrons jump to a higher orbital depend on?

A

the central ion

its oxidataion state

the coordination number

size of the energy gap

34
Q

what does the colour of compounds depend on?

A

the complement of those that are absorbed

when visible light hits a transition metal ion all the same energy, some frequencies are absorbed when electrons jump up to higher orbitals
the frequencies absorbed depend on the size of the energy gap

the rest of the frequencies are transmitted or reflected

  • these frequencies combine to make the complement of the colour of the absorbed
  • this is the colour you see
35
Q

origin of no colour - what if no 3d electrons or 3d sub-level is full?

A

no electrons will jump

so no energy absorbed

if no energy absorbed, the compound will look white or colourless

36
Q

transition metals - why do they make good catalysts?

A

because they can change oxidiation states by gaining or losing electrons within their d-orbitals

they can transfer electrons to speed up reactions

37
Q

transition metals - why are catalysts good?

A

good for industry and for environment

they allow reactions to happen faster and at lower temperatures and pressures reducing energy usage

38
Q

transition metal catalysts - why can they pose health risks? (examples)

A

their compounds are toxic

copper - can damage liver and kidneys

manganese - can cause psychiatric problems

39
Q

transition metal catalysts - why can they pose health risks? (examples)

A

their compounds are toxic

copper - can damage liver and kidneys

manganese - can cause psychiatric problems

40
Q

what type of catalyst are transition metals?

A

heterogeneos and homogeneous

41
Q

transition metal catalysts - why are they heterogeneous?

A

its in a different phase from the reactants

  • good because they can use their s- and d- orbirals for bonding to the reactant molecules
42
Q

transition metal catalysts - heterogeneous mechanism (3 stages)

A
  1. the reactant molecule are attracted to the surface of the catalyst and stick to it
    - ADSORPTION
  2. the surface of the catalyst activates the molecules so they react more easily
    - interactions weaken the bonds in the molecule making it easier to break and reform as products
  3. the product molecules leave the surface of the catalyst making way for fresh reactants to take their place
    - DESORPTION
43
Q

transition metal catalysts - what makes a good heterogeneous catalyst?

A
  1. attract reactant molecule strongly enough so that they are held to the surface long enough to react
  2. not attract the product molecules to strongly
    - otherwise the molecules wont deabsorb and will block the catalyst from fresh reactants
44
Q

heterogeneous transition metal catalyst - Iron example

A

iron catalyses the reaction of nitrogen and hydrogen to make ammonia
- HABER PROCESS

45
Q

heterogeneous transition metal catalyst - CuSO4 example

A

catalysed reaction of zinc with acids

46
Q

heterogeneous transition metal catalyst - MnO2 example

A

catalyses decomposition of hydrogen peroxide

47
Q

why do transition metals make good homogeneous catalysts?

A

because transition metals have variable oxidation states

in the same physical state as reactants (usually (aq))

48
Q

homogeneous transition metal catalysts - mechanism

A

work by combining with the reactants to form an intermediate species which then reacts to form the products

  • and reform the catalyst

the activation energy needed to form the intermediate (and form products from the intermediate) is lower than that needed to make the products directly from the reactants