Transition Elements A2 Flashcards
Why is the d block called the d block?
Because the highest energy electrons are in the d subshell.
What is a transition element?
A d block element that forms an ion with an incomplete d-subshell.
What elements found in the d block are not transition elements?
Scandium and Zinc.
Sc’s only ion is Sc3+ (empty sub-shell).
Zn’s only ion is Zn2+ (full sub-shell).
What are the physical properties of transition metals? Explain.
- Good conductors of heat and electrcity.
- Hard, strong and shiny
- High b.p and m.p
Hardness and high m.p and b.p is due to strong metallic bonds.
Both 4s and 3d available to take place in delocalisation into a ‘sea of electrons’ - giving strong metallic bondings and ability to conduct electricity.
What are the chemical properties of transition metals?
- Variable in oxidation state
- Colour
- Catalysts
- Complex formation
Why do TMs have variable oxidation states?
TMs can use both 3d and 4s electrons in bonding. This means they can form ions of roughly the same stability by losing different numbers of electrons.
For what 2 reasons do TMs make efficient catalysts? Give an example of a process catalysed by a transition metal.
- 3d electrons enable TMs to form temporary bonds so reactants are held in place.
- As they have several oxidation states they can participate in electron transfer processes, thus providing an alternative route for the reaction.
e.g. Contact process
2SO2 + O2 <–> 2SO3
Catalysed by Vanadium (V) oxide
How can you simplify writing the electron structure for transition elements?
Writing [Ar] and carrying on from there.
What are complex ions?
When species called Ligands form coordinate (dative) bonds to a central metal ion.
What is a ligand?
A molecule or ion that can donate a pair of electrons to a central metal ion to form a coordinate bond.
What is the coordinate number?
The total number of coordinate bonds formed between a central metal ion and its ligands.
What are ligands with one / two coordinate bonds called?
Monodentate
Bidentate
What usually are the shape of complexes with H2O or NH3?
Octahedral
What shape are 4-coordinate complexes?
What is the exception?
Square planar
Complexes with 4 Cl- are tetrahedral due to it’s larger size.
Complex ions can also show 2 types of stereoisomerism. What are they?
Cis-trans isomerism - for both monodentate and bidentate
Optical Isomerism