Transition Metals Flashcards
What are the two exceptions for electron configurations?
Copper and chromium’s sub shells fill differently
Why is 4s filled before 3d
It has a lower energy level most of the time
Does the 3d or the 4s orbital lose electrons the quickest?
4s will lost electrons first
Define transition metal
A transition metal is one which forms one or more stable ions which have incompletely filled d orbitals.
Why are scandium and zinc sometimes considered not to be transition metals?
- They form white solids and colourless solutions
- They have little catalytic activity
- Don’t have varying oxidation states
What are some properties of transition metals?
- Hard metals with high melting and boiling points
- ions form coloured solutions
- Varying oxidation states
- Act as catalysts
- Form complex ions
Define a ligand
A species with a lone pair of electrons which can form a dative covalent bond with a central transition metal ion
How do complex ions form?
Form complex ions in water due to the space in the 3d orbital
What’s a coordinate number
The number of species a central atom can hold as its nearest neighbours in a complex compound
What bond forms between the transition metal ion and water?
A dative covalent bond.
What happens when a transition metal goes into a aqueous solution?
The 5 3d orbitals split
What causes colours to form in aqueous solutions of transition metals?
Electrons absorb light of a specific energy and frequency (equal to the difference in the split 3d orbitals) causing them to excite. The colour we see is the wavelength of the light complimentary to the wavelength absorbed.
When do you use the Latin name of copper and what is it?
When the complex is negatively charged
Cuprate
What colour is vanadium +2
Violet
What colour is vanadium +3
Green
What colour is vanadium oxide +2 (VO+2)
Blue
What colour is chromium +3
Green with OH- ions but violet with ammonia.
What colour is dichromate ions (Cr2O7)
Orange
What colour is iron +2 (Fe +2)
Pale green
What colour is iron +3 (Fe +3)
Yellow
What colour is Cobalt +2 (CO +2)
Pink
What colour is copper +2
Blue
What is a complex ion?
A central transition metal ion is surrounded by ligands bonded by dative covalent bonds
What’s a bidentate ligands?
A ligands with 2 lone pair of electrons
What’s special about EDTA -4
It can form 6 coordinate bonds
What are three examples of small ligands which fit 6 coordinate bonds?
H2O:
:NH3
:OH-
What shape and how many bonds would chlorine make with the central transition metal?
Tetrahedral (109.5)
4 bonds
What’s an example of a really large ligand (forms less than 4 bonds)
Ethandioate
Ethanediamine
EDTA
What’s the only tetrahedral exception for 4 ligands bonds.
2 ammonia ions and 2 chloride ions
Square planar instead
What’s the equation to find the oxidation state of the metal ion.
Total oxidation state - total oxidation state of ligand
Do complex ions show stereoisomerism?
They can show optical isomerism and E/Z isomerism depending on the ligands bonded
Explain why complex ions are coloured.
- The d orbitals split when in a solution.
- Difference in energy between levels depends on the ligand
- Difference leads to different wavelength of light absorbed
- The unabsorbed photons are reflected
What’s the colour of VO2 (+1)
Yellow
What colour is Cr+2 ?
Blue
What is a monodentate ligand?
A ligand which can form one coordinate bond per ligand
Where are the six donor sites on EDTA -4
4 on the oxygens and 2 on the nitrogens
Why does a complex change colour when the ligand is changed?
The energy split between the d-orbitals change so the frequency of light absorbed and reflected changes.
What shape do transition metal ions form with small ligands?
Octahedral
How can you increase the oxidising power of transition metals with low oxidation states?
Put them in an alkaline solution.
Explain the steps of writing out half equations in alkaline conditions.
-Add H2O to balance out O
-Add H+ to balance out H
- Add OH- to both side to cancel out H+
- Add OH- and H+ together to form H2O
When you add acid to chromate ions what form and what’s the colour change?
Forms dichromate ions
Yellow to orange
When you add alkali to dichromate ions what form and what’s the colour change?
Chromate forms
Orange to yellow
Why is the acidity of [M(H2O)6]+3 greater than [M(H2O)6)+2?
The +3 ions have higher charge density and have greater polarising power. The greater the polarising power the more strongly it attracts the water molecule. This weakens the O-H bond so it breaks more easily releasing H+ ions.
What transition metal complex is amphoteric?
Metal hydroxides with chromium and aluminium
[M(H2O)3(OH-)3]
Define catalyst.
A substance that can speed up a reaction by providing an alternative pathway with a lower activation energy where none of the catalyst is used up.
What’s a heterogenous catalyst?
A catalyst which is in a different state/phase to the species in the reaction.
How do solid catalysts work?
Adsorb molecules onto active sites on the surface of the catalyst. These increase the proximity of molecules and weaken the covalent bonds so reactions occurs more easily.
What happens to a solid iron catalyst when sulfuric impurities react?
The catalyst is poisoned by impurities which blocks the active sites and prevents absorption.
What’s a homogenous catalyst?
Catalysts which are in the same phase to the species in the reaction.
What is autocatalysis?
When a product can act as a catalyst for the reaction.
How do heterogenous catalysts work ?
Reactants are absorbed in the active sites of the catayst which causes the bonds in the reactants to weaken enough to react. After reacting it is deabsorbed leaving the catalyst uneffected.
What is used to measure E cell value?
A voltmeter
What chemical is a salt bridge made from?
NaCl
Why can’t a salt bridge be replaced by an unreactive metal wire?
Wire doesn’t allow flow of ions
What colour is VO3
yellow
