- monodentate (one lone pair) - bidentate ligand (two lone pairs)

Transition metals Flashcards by darya .

define transition metal

A d-block element that forms at least one ion with a partially filled d-subshell

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which transition metals are exceptions to the 4s filling before 3d

chromium and copper

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electronic configuration of chromium (24e-)

1s2 2s2 2p6 3s2 3p6 3d5 4s1

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electronic configuration of copper (29e-)

1s2 2s2 2p6 3s2 3p6 3d10 4s1

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what are the three properties of transition metals

variable oxidation states
formation of coloured compounds
act as catalysts

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variable oxidation states of iron

Fe2+ and Fe3+

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variable oxidation states of copper

Cu+ and Cu2+

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variable oxidation states of chromium

Cr2+, Cr3+, Cr6+

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coloured compounds of vanadium

V2+ = purple
V3+ = green
V4+ = blue
V5+ = yellow

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coloured compounds of chromium

Cr2+ = blue
Cr3+ = green
Cr6+ = orange

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coloured compounds of iron

Fe2+ = pale green
Fe3+ = yellow

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coloured compounds of manganese

Mn2+ = pale pink
Mn4+ = brown
Mn6+ = green
Mn7+ = purple

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examples of transition metals as catalysts

Iron in haber process
Zinc in hydrogenation
Manganese oxide (MnO2) in hydrogen peroxide decomposition

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define ligand

a molecule or ion that donates a pair of electrons to a central metal ion to form a co-ordinate bond

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types of ligand

monodentate (one lone pair)
bidentate ligand (two lone pairs)

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examples of monodentate ligands

H2O, Cl-, NH3

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examples of bidentate ligands

1,2-diaminoethane (en)
ethanedioate ion

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define co-ordination number

the number of coordinate bonds formed with the central metal ion

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shapes of complex ions

tetrahedral
octahedral
square planar

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describe octahedral complex ions

coordination number = 6
bond angles of 90

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describe tetrahedral complex ions

coordination number = 4
bond angles of 109.5

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describe square planar complex ions

coordination number =4
bond angles of 90

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what determines whether a complex ion is tetrahedral or square planar if there are 4 ligands

square planar occurs in complex ions with central metal ions with 8 or more d electrons in their outermost subshell

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what complex ions is cis/trans isomerism seen in

octahedral and square planar

cis/trans isomerism in square planar

- 2 identical ligands - same plane = cis (90 degrees) - opposite planes = trans (180 degrees)

cis/trans isomerism in octahedral

- 4 identical monodentate ligands - or 2 bidentate and 2 monodentate

give an example of a square planar complex ion that displays cis/trans isomerism

[Pt(NH3)2Cl2] cis/trans platin

uses of cisplatin

used as an anticancer drug as it binds to DNA preventing cell division

what complex ions is optical isomerism seen in

cis isomers of octahedral complex ions that have 2 or more bidentate ligands ONLY

what is a ligand substitution reaction

when a ligand in a complex ion is replaced with another

ligand substitution of hexaaqua copper (ii) with excess aqueous ammonia

[Cu(h2O)6]2+ + 4NH3 --> [Cu(NH3)4(H2O)2]2+ + 4H20

ligand substitution of hexaaqua copper (ii) with excess conc HCL

[Cu(h2O)6]2+ + 4Cl- ⇌ [CuCl4]2- + 6H2O

why is there a shape change when hexaaqua copper undergos ligand substitution with chloride ions

chloride ligands are larger than water ligands

what is the colour change when hexaaqua copper undergoes ligand substitution with excess ammonia

pale blue solution to dark blue solution

what is the colour change when hexaaqua copper undergoes ligand substitution with LIMITED ammonia

pale blue solution to a pale blue precipitate of Cu(OH)2

what is the colour change when hexaaqua copper undergoes ligand substitution with excess concentrated HCl

pale blue solution to yellow solution

ligand substitution of hexaaqua chromium (iii) with excess aqueous ammonia

[Cr(H2O)6]3+ + 6NH3 --> [Cr(NH3)6]3+ + 6H2O

what is the colour change of ligand substitution of hexaaqua chromium (iii) with excess aqueous ammonia

violet solution to purple solution

what is the colour change when hexaaqua chromium undergoes ligand substitution with LIMITED ammonia

violet solution to green grey precipitate of Cr(OH)3

haemoglobin and ligand substitution

central Fe2+ ion forms a coordinate bond with H2O that can undergo ligand substitution with O2 in high o2 partial pressures CO can also but this doesnt unbind easily so limits the O2 transported around the body

general formula of transition metal precipitation reactions

X^n+(aq) + nOH-(aq) --> X(OH)n (s)

colour change of Cu2+ in NaOH

blue solution --> blue precipitate

colour change of Fe2+ in NaOH

pale green solution --> pale green precipitate

colour change of Fe3+ in NaOH

yellow solution --> orange/brown precipitate

colour change of Mn2+ in NaOH

pale pink solution --> light brown precipitate

colour change of Cr3+ in limited NaOH

violet solution --> grey/green precipitate

colour change of Cr3+ in excess NaOH

violet solution --> dark green solution

formula of Cr3+ in limited NaOH

Cr3+(aq) + 3OH-(aq) ---> Cr(OH)3(s)

formula of Cr3+ in excess NaOH

Cr(OH)3(s) + 3OH-(aq) --> [Cr(OH)6]3-(aq)

what happens to Fe(OH)2 in air

oxidised to Fe(OH)3 colour change green ppt --> orange/brown ppt

precipitation reactions with ammonia general formula

X^n+(aq) + nNH3(aq) --> X(OH)n(s) + nNH4(aq) colour changes are the same

precipitation of Cu2+ with excess ammonia

[Cu(H2O)6](aq) + 4NH3(aq) --> [Cu(NH3)4(H2O)2]2+(aq) + 4H2O(aq)

precipitation of Cr3+ with excess ammonia

[Cr(H2O)6](aq) + 6NH3(aq) --> [Cr(NH3)6]3+(aq) + 6H2O(l)

what is the complex ion that X(OH)n is reffering to

[X(OH)n(H2O)6-n]

precipitation of Cu2+ with limited ammonia

[Cu(H2O)6]2+(aq) + 2NH3(aq) --> Cu(OH)2(s) + 2NH4+(aq)

precipitation of Cu2+ with limited ammonia colour change

pale blue solution to pale blue precipitate

precipitation of Cr3+ with limited ammonia

[Cr(H2O)6]3+(aq) + 3NH3(aq) --> Cr(OH)3(s) + 3NH4+(aq)

precipitation of Cr3+ with limited ammonia colour change

violet solution to grey/ green precipitate