1.4 Transition Metals Flashcards
transition metal
metals with an incomplete d subshell in at least one of their ions
metals with an incomplete d subshell in at least one of their ions
transition metal
when are TM ions formed
TMs losing electrons from the 4s orbital
properties of TMs
- have atoms or ions with an incomplete d subshell (except Zn 2+)
- can form complexes
- have variable oxidation states (numbers)
- form coloured ions
- show catalytic ability
transition metal complex
a central metal ion surrounded by ligands
oxidation number
the charge on the ion if the element was isolated
rules for finding oxidation numbers
- oxidation number of an uncombined element is 0
- for monatomic ions, the oxidation number is the same as the charge on the ion
- oxygens oxidation number is -2
- hydrogens oxidation number is +1, however in metallic hydrides it is -1
- the sum of all the oxidation numbers of all the atoms in a molecule or neutral compound must add up to 0
- the sum of all the oxidation numbers of all the atoms in a polyatomic ion is equal to the charge on the ion
oxidation
increase in oxidation number
increase in oxidation number
oxidation
reduction
decrease in oxidation number
decrease in oxidation number
reduction
what happens to oxidising agents
they are reduced
what happens to reducing agents
they are oxidised
oxidation agents value
oxidation number >3
ligand
a molecule or negatively charged ion with electron pairs available for dative covalent bonding
monodente
donates 1 electron pair to a metal ion
bidente
donates 2 pairs of electrons to a metal ion
quadridente
donates 4 pairs of electrons to a metal ion
hexadente
donates 6 pairs of electrons to a metal ion
what can ligands be
- negative ions (OH-)
- molecules with non-bonding electrons (NH3)
coordination number
the total number of bonds from the ligands to the metal ion
the total number of bonds from the ligands to the metal ion
coordination number
coordination number 2 shape
linear
coordination number 4 shape
square planar
or
tetrahedral
coordination number 6 shape
octahedral
how to write TM complex
the symbol of the TM is written first, followed by the symbols of the ligands in alphabetical order according to which atom binds. for water, OH2 is used since the oxygen atom binds to the metal
naming TM complexes rules
- ligands are named in alphabetical order followed by the name of the metal and its oxidation state. if there is more than one of a ligand, it is preceded by the prefix; di, tri, tetra, etc.
- if the ligand is a negative ion ending in -ide, the ligands name will change to end in ‘o’. chloride becomes chlorido and so on.
- ammonia (NH3) becomes ammine, water becomes aqua, carbon monoxide becomes carbonyl, iodine becomes iodido
- only if the complex ion is overall negative, the name of the complex ends in -ate. however, copper becomes cupprate and iron becomes ferrate.
- if the complex ion is a salt, the name of the positive ion precedes the name of the negative ion
TM forming ions d orbitals
the d orbital splits into three degenerate lower energy levels and two higher energy, less stable, levels
what does d orbital splitting result from
from repulsion from electrons in the ligand
d-d transitions
- if sufficient energy is provided, an electron can be promoted from a lower d orbital to a higher d orbital
- the energy gap between these d orbitals corresponds to a wavelength in the visible region and therefore a colour
when is a TM ion colourless
- the d orbital is completely full
→ there is no where for the electrons to be promoted to- the d orbital is completely empty
→ there are no electrons to be promoted
- the d orbital is completely empty
ligands and splitting
different ligands will create different splits
- strong field ligands create a large split
- weak field ligands create a small split
homogeneous catalyst
a catalyst in the same physical state as the reactants
a catalyst in the same physical state as the reactants
homogeneous catalyst
heterogeneous catalyst
a catalyst in a different physical state to the reactants
a catalyst in a different physical state to the reactants
heterogeneous catalyst
why are TMs good catalysts
transition metals with unpaired electrons or unfilled d orbitals allow intermediate complexes to form. the variable oxidation states of TMs allow them to be involved in the reaction to catalyse it but then be regenerated at the end
[Fe(OH2)6]2+
i) Name this complex.
ii) What is the coordination number of the transition metal ion?
iii) What is the oxidation state of the metal ion?
i) Hexaaquaferrate(II)
ii) 6
iii) +2
[CrF4]-
i) Name this complex
ii) What is the coordination number of the transition metal ion?
iii) What is the oxidation state of the metal ion?
i) tetrafluorochromate(III)
ii) 4
iii) +3
[Cu(CN)6]4-
i) Name this complex
ii) What its coordination number of the transition metal ion?
iii) What is the oxidation state of the metal ion?
i) hexacyanocuprate(II)
ii) 6
iii) +2
if a complex is colourless, it absorbs ____
uv light
oxidation state of sulphur in SO4^2-
+6
oxidation state of nitrogen in NO3^-
+5
oxidation state of manganese in MnO4^-
+7
oxidation state of cobalt in [Co (NH3)6]2+
+2
name [Cu(H20)6]Cl2
hexaaquacopper (II) chloride
name [Co(NH3)6]F2
hexaamminecobalt (II) flouride
charges of different ligands
- CN has a -1 charge
- Cl, I, etc has a -1 charge
- C2O4 has a -2 charge
- NH3 is neutral
- H2O is neutral
- CO is neutral
- OH is -1
- O is -2
- H is +1
name K2[Fe(H20)2(CN)4]
potassium diaquatetracyanidoferrate (II)
name [Co(NH3)4Cl2]Cl
tetraamminedichloridocobalt (III) chloride
name Mg[Pt(CO)2(C2O4)2]
magnesiumdicarbonyldioxalatoplatinate (II)
Cr(NH3)5(H2O)3 (NO3^-)
pentaammineaquachromium (III) nitrate
write amminetetraaquachromium (II)
[Cr(NH3)(H2O)4]2+
write silver (I) tetraiodidomercurate (II)
Ag2[Hg(I)4]2-
write amminepentachloridocuprate (II)
[Cu(NH3)(Cl)5]3-
write pentaamminechloridocobalt (III) sulfate
[Co(NH3)5(Cl)]^2+ SO4
write potassium diaquatetracynadioferrate (III)
K [Fe(H2O)2(CN)4]1-
explain how a TM complex can be colourless
Full or complete d subshell
It only absorbs ultraviolet/UV light
Analytical technique to determine the presence of ions in a sample
Flame test or atomic absorption
