18 - Transition elements Flashcards
What is a transition element?
A d-block element that forms an ion with an incomplete d sub-shell
Which elements in d-block aren’t transition metals?
Scandium and zinc
Why is scandium not a transition metal?
Forms Sc 3+ meaning the d sub-shell is empty
Why is zinc not a transition metal?
Only forms Zn 2+ so it has only full d-subshells
What are the exceptions to the spin pair distribution of transition metals? Explain
Chromium and copper only have 4s^1 and have an extra one in 3d instead
What is different about the appearance of different ions for the same element?
They have different colours
Why do ions actually have colours?
Light is absorbed and we see the colours not absorbed
What happens to white solids when they form solutions?
The solution is always colourless
What are the 3 properties of TRANSITION metals?
Different oxidation states
Act as heterogeneous catalysts
Different colours
What is the contact process and what is the catalyst?
2SO~2 + O~2 –> 2SO~3
With V~2 O~5 catalyst
What is the catalyst for reacting zinc with an acid?
Cu 2+ catalyst
Define ligand
A ligand is a molecule or ion that can donate a pair of electron to form a dative covalent bond with a transition metal
What is the condition to be a ligand?
Must have lone pairs of electrons in the outer energy level. These are used to form co-ordinate bonds with the metal ion.
All ligands are lone pair donors
Define complex ion
A transition metal ion bonded to one or more ligands by dative covalent bonds
What is coordination number?
Number of dative bonds to central ion
What is a monodentate ligand?
Where only one atom in the ligand has a lone pair
It only bonds to the central ion with one bond
What are the 6 main ligands and what are their oxidation numbers?
H~2 O is 0
NH~3 is 0
SCN (thiocyanate) is -1
CN (cyanide) is -1
Cl- is -1
OH- is -1
How do you write the formula of a complex ion?
e.g. Copper(II) ion with one OH and 5 water ligands.
A copper(II) ion with one OH and 5 water ligands is:
[Cu OH (H~2 O)~5] +
The +ve charge is the sum of all charges in complex ion
When there are 4 ligands, what shape is formed?
Tetrahedral
What is the exception to the tetrahedral, 4 ligand idea?
Nickel, platinum, palladium and gold make a square planar shape instead
What are Cis and Trans complex ions?
When you have multiple ligands of 2 different types of molecule
Trans is where the same group ligands are opposite each other in the shape
Cis is where this isn’t true
What is Cis-platin?
A very effective cancer drug which binds to DNA
What are bidentate ligands?
Ligands that form 2 different dative bonds with the central ion
What is the name and charge of C~2 O~4?
Ethanedioate with a 2- charge
What type of ligand is ethanedioate?
A bidentate ligand
What is EDTA?
A hexadentate ligand with 6 lone pairs
Give 4 uses of EDTA
Reduces water hardness
Food stabiliser
Prevents clotting if needed in medical procedures
Treats lead or mercury poisoning
What are optical isomers?
Complex ions which are mirror images of each other
They are actually different
which isomers (cis or trans) have optical isomers
Only Cis have optical isomers
What does haemoglobin do?
Transfers oxygen into body and carbon dioxide out
How does haemoglobin work?
The oxygen and carbon dioxide act as ligands to the haemoglobin
What is haemoglobin with oxygen called?
Oxyhaemoglobin
Why can the oxygen and carbon dioxide detach and attach to the haemoglobin so easily?
The bond that they attach to is weak
How does carbon monoxide harm people?
Carbon monoxide acts as a ligand and bonds to the haemoglobin
But the bond is strong when it is CO so it is very hard to detach the CO
What are the 2 half equations for the following reaction:
2Al + Fe~2 O~3 –> 2Fe + Al~2 O~3
Al –> Al 3+ + 3e-
Fe 3+ + 3e- –> Fe
If you know that one of the reactants is MnO~4 - and one of the products is Mn 2+
Show how you work out the equation step by step
Firstly, you ALWAYS balance the oxygens by putting H~2 O’s on the other side:
MnO~4 - –> Mn 2+ + 4H~2 O
Now you balance the hydrogens by putting H+ on the other side
MnO~4 - + 8H+ –> Mn 2+ + 4H~2 O
You then count the oxidation numbers and put electrons in to balance the oxidation numbers:
MnO~4 - + 8H+ + 5e- –> Mn 2+ + 4H~2 O
