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chemistry > topic 15- transition metals > Flashcards

topic 15- transition metals Flashcards

1
Q

d block elements

A

less sharp differences
similarities across periods are greater

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2
Q

chromium and copper

A

fills d orbital before s
arrange so have the lowest energy
less repulsion

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3
Q

ion formation

A

when loose or gain an electron it is lost/gained from 4s first so it is written second rather than first

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4
Q

what are transition metals
-def
-characteristics

A

dblock element which forms one or more stable ions with incomplete d orbitals
-hard solids
-high melting and boiling
-catalst
-coloured ions and compounds

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5
Q

ligands

A

species bonded to the metal ion by co-ordiate bonds (dative)
donate a pair of electrons to metal ions
transition metals with ligins are complex ions that carry a charge

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6
Q

coordination number

A

number of cooridinate bonds from the ligands to the central metal ions

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7
Q

types of ligands

A

monodentate - single lone pair
bidentate - two lone pairs
-1,2-diaminoethane
multidentate - multpiple lone pairs
-EDTA (ethylenediaminetetraacetic acid)

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8
Q

chelates

A

transition metals held in claw - the bond

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9
Q

naming complex ions

A

number of ligins prefix
-mono di tetra
name the ligands ending in o for ions
- chloro hydroxo
amine for NH3 and aqua for H2O
name the central metal ion
neutral and positive - naomal name
negative - latinaised name + ate
add oxidation number for central metal

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10
Q

octahedral

A

coordination number of 6

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11
Q

tetrahedral

A

4

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12
Q

sqaure planar

A

4
cistrans isomerism
e.g cis-platin trans-platin
-cis can be used in cancer treatment but trans cannot

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13
Q

linear

A

2

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14
Q

equation linking energy and frequency of light

A

ΔE = h𝝂
where ΔE = change of energy
h = Planck’s constant
𝝂 = frequency

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15
Q

what makes colours of transition metals

A

d orbitals split due to ligands
electrons absorb light in the visible region of the spectrum
to promote electrons to higher energy levels
the unabsorbed light is the colour shown/reflected

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16
Q

stability of complexes

A

comparison of stabilities of two complexes where the number of ligands has changed

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17
Q

types of reaction of ligands

A

redox
acid base
ligand exchange
coordination number change

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18
Q

types of reaction of ligands
-redox

A

the oxidation number of the transition metal ion changes
-Fe+ (aq) is pale green but when exposed to air turns yellow
+2 to +3

19
Q

types of reaction of ligands
-acid base reaction

A

one or more of the ligands gains or looses a hydrogen ion
-hexaaquacopper ions react with hydroxide ions OH- remove hydrogen ions from water ligands attached to copper in acid base
isoluble neutral complex formed - blue precipitate

20
Q

types of reaction of ligands
-ligand exchange

A

one or more of the ligands around the central transition metal is replaced by a different ligand
-when excess amonia is added to hexaaquacopper ions ligand exchange occurs deep blue solution of tetraaminediaquacopper formed

21
Q

types of reaction of ligands
-coordination number change

A

the number of ligands changes
-conc hcl added to hexaaquacopper the six water are replaced by four chlorine
blue to green to yellow
coordiantion 6-4

22
Q

haemaglobin

A

in a haem group 4 n atoms hold Fe2+ ion by forming dative bonds in the square planar structure
fifth dative bond from protein to Fe2+ ion
oxygen binds by becoming ligand to Fe2+
-reversible reaction as bond is weak

23
Q

carbon monoxide

A

lone pair on carbon that forms ligand
strong bond between carbon and oxygen so takes oxygen from Fe2+
-ligand substitution
non reversible reaction

24
Q

amphoteric reaction

A

ability of a species to react with both acid and bases

25
Q

cobalt complexes reaction with alkali

A

sodium hydroxide to hexaaquacobalt
-pink solution forms blue precipitate
-acidbase reaction
-two hydroxide removed two hydrogen from water ligands and converted into water molecules
ammonia and hexaaquacobalt
-same reaction
-when ammonia used in excess the precipitate dissolves to form brown solution - ligand exchange

26
Q

cobalt complexes with hcl

A

conc hcl and hexaaquacobalt
pink to blue
-ligand exchange
-change in coordination number

27
Q

iron ii complex with alkali

A

sodium hydroxide to hexaaquairon(ii)
-pale green sol forms green precipitate
-acid base
-water mol that lost hydrogen ions are now hydroxide ligands
ammonia to hexaaquairon(ii)
-same observations
-when left standing the green gradualy changes to brown

28
Q

reaction of iron iii complexes with alkalis

A

sodium hydroxide to hexaaquairon(iii) ion
-yellow-brown sol forms brown precipitate
acid base oh- remvoes 3 water ligands and converted into water molecules
-now hydroxide ligand
aqueous ammonium to hexaaquairon(iii)
-same observations

29
Q

shapes of ligand complexes

A

no of dative bonds
shape
move to minimise repulstion

30
Q

cromium ion with water

A

hydrogen ion is lost from a water ligand
forms hexaaquachromium
water is a base
complex ion is acid

31
Q

chromium ion with hydroxide

A

hydroxide remove H+ from water ligands
three hydrogens removed
forms complex ion with no charge
-neutral complex
insoluble in water and precipitate formed
reaction will continue

32
Q

chromium with ammonia

A

ammonia acts as a base and a ligand
green sol > green precip > violet solution

33
Q

oxidation of chromium iii to chromium vi

A

excess of sodium hydroxide added to hexaaquachromium iii
to form green hexahydroxochromate iii ions
then oxidised by warming with hydrogen peroxide sol forms bright yellow sol of chromate vi ions

34
Q

chromium vi to hexahydroxochromate

A

add dilute sulfuric acid to yellow to form orange

35
Q

equilibrium shift

A

increae hydrogen - side with least gas particles
increase hydroxide -side with most hydrogen ions as reacts with them so moves to replace

36
Q

drichromate vi with zinc and acid

A

e.g pottasium dichromate
can be reduced to chromium iii to chromium ii
needs to allow hydrogen out but stop oxygen getting in
-can use cotton wool

37
Q

pottasium dichromate is used for

A

seconadary alcohols to keytones
primary alcohols to aldehydes
primary alcohols to carboxylic acids

38
Q

oxidation states of vanadium

A

+5-yellow/-VO2^+
green as mixture of yellow and blue
+4-blue-VO^2+
+3-green-V^3+
+2-violet-V^2+

39
Q

reduction agent vanadium

A

has to be more negative than all the steps in order to occur

40
Q

hetrogenous catalyst

A

reactions adsorbed onto surface on active sites
weaken bonds
change orientation
products deadsorb
can have too high or too low adsorbtion

41
Q

catalyst poisioning

A

other substances adsorb onto surface blocking active sites
hard to remove

42
Q

homogenous catalysts

A

mostly reactions in solution
catalyst reacts to form intermediate
forms a product faster than the original and regenerates catalyst

43
Q

transition metal catalysts

A

works by varying oxidation state

chemistry (25 decks)

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