13.1 Transition metals (HL) Flashcards
Valency, charge and oxidation state of Copper in CuSO4
Valency= 2 Charge= 2+ Oxidation= +2
Transition element
Element that forms atleast one stable ion with a partially filled d subshell
Why is Scandium considered a transition element and why is this controversial?
Its configuration is [Ar] 3d1 4s2. This means that Sc2+ has an incomplete d subshell and hence is a transition element. However, it largely reacts as Sc3+ which means it doesn’t have a partially filled d subshell and that’s why its still debated.
Is Zinc a transition metal and why or why not?
It is NOT a transition metal as both atom and ion (Zn2+) have a complete 3d sub shell
Is Copper a transition metal?
Yes. Even though Cu and Cu+ have complete d subshells, Cu 2+ has an incomplete d sub shell
What does the presence of unpaired electrons result in?
- Variable oxidation states
- Colored compounds
- Possible catalytic activity
- Formation of complex ions in solution
- Possible magnetic properties
Calculate oxidation state of Mn in KMnO4
K= +1
O= -2 so O4= -8
–> 1+x-8=0 so x= +7
What is the variable oxidation state that most transition elements have and why?
+2 except Scandium because they lose the 2 4s electrons first
Why does variable oxidation state occur?
Because of the closeness of energy between 3d and 4s subshells. There is little change in atomic radii and less effective nuclear charge as electrons are added to 3d sublevel resulting in lower range of ionization energies. This allows them to lose electrons easily
What are the variable oxidation states for Magnesium and why?
+2 only as it is in Group 2 so there is a large increase between 2nd and 3rd ionization energy. Therefore Mg cannot have +3
What are the variable oxidation states for Titanium and why?
Large increase between 4th and 5th ionization energy so only +2, +3 and +4 (as +5 would require too much energy to remove)
Why do transition metals have higher charge density and what does it do?
They are smaller than other elements. In solution, this high charge density attracts water molecules to form coordinate bonds with positive ions
Complex ion
Formed when ligands bond to a central metal ion
Ligand
Species with lone pair of electrons that act as a Lewis Base (they donate lone pair)
Central metal ion
Acts as Lewis Acid as it accepts lone pair and forms coordinate covalent bond
Coordination number
No. of coordinate covalent bonds between ligand and metal ion
What types of ligands are there?
Neutral ligands (H2O, NH3) or charged ions (Cl-, CN-)
What is a ligand that forms one coordinate covalent bond (only one pair of electrons involved)?
Monodentate ligand like H2O
Besides monodentate ligands, what others exist?
Bidentate, polydentate and hexdentate
What are the shape of most complexes?
Octahedral
4 types of shapes for complexes and the number of bonds in each
Linear (2)
Square planar (4)
Tetrahedral (4)
Octahedral (6)
What is oxidation state of Fe in [Fe(H2O)6]2+?
H2O is neutral so Fe must be +2
What is oxidation state of Ni in [Ni(CN)4]2-?
CN has charge of 1- so x+(-1*4)= 2- hence Ni =+2
What is a coordination compound?
Complex ion + counter ion
Counter ion
Balances out charge of complex ion
How can you neutralize [Fe(H2O)6]3+ with Cl?
Add 3 Cl- ions so it will become coordination compound –> [Fe(H2O)6]Cl3
Why can’t CH4 be a ligand?
Because it has no lone pair of electrons
What is dimagnetism?
When a substance only has paired electrons as opposite spin cancels out magnetic effect. Weak repulsion means non-magnetic eg. Zinc
What is paramagnetism?
When a substance has atleast one half-filled orbital. Opposite spin shows attraction and hence magnetic effect.
Is paramagnetic effect permanent?
No. Magnetic properties are not retained when external field is removed
Which shows more attraction and why? MnO2 or Cu(NO3)2
- MnO2 will be more magnetic as:
- Mn will have charge of 4+ so config is [Ar] 3d3
- Cu will have charge of 2+ so config is [Ar] 3d9
- Mn has 3 unpaired orbitals while copper only has 1
- More unpaired orbitals= more attraction
What do catalysts do?
They allow reactions to occur at lower temperature and pressure
Heterogenous catalysts
When catalyst is in a different state than reactants
Example of heterogenous catalyst
Haber process: Iron is solid but nitrogen and hydrogen are gaseous. Iron provides surface for absorption of gases and allows them to orient themselves to react
Homogenous catalysts
Same physical state as reactants
Why are homogenous catalysts effective in redox reactions?
Because of variable oxidation states
Examples of homogenous catalysts
- Enzymes: Iron and Cobalt
- O2 in transport: Iron is central to heme group
- Vitamins: Co(III) ions are in B12
