Module 5 - [ch24] Transition elements Flashcards
What are transition elements?
D-block elements that form at least 1 ion with a partially filled d-orbital
Which elements are in the D-block but not transition metals. Why?
Zinc and Scandium
Zn / Sc
Zinc has a full filled D-orbital
Scandium’s ion (Sc3+) has an empty D-orbital
What are 3 properties of transition metals
Form coloured compounds
They form compounds in which the transition elements has different oxidation states - variable oxidation states
The elements and their compounds can act as catalysts
What is a catalyst
A substance that can be used to increase the rate of reaction without being used up
How do catalysts increase the rate of reaction
They provide an alternative reaction pathway with a lower activation energy
Give two examples when transition metals are used as catalysts
Haber process - nickel catalyst
Contact process - Vanadium Oxide
What is the difference between homogenous and heterogenous catalysts?
Homogenous - when the catalyst is in the same physical state as the reactants
Define Ligand
Molecule or ion that donates a lone pair of electrons to a central metal ion to form a co-ordinate bond
what is a co-ordinate bond
a dative bond
where both electrons involved in the bond are donated from one of the bonded atoms
What is a co-ordination number
The number of co-ordinate bonds attached to the central metal ion
How are complex ion formed
When one or more molecules or negatively charged ions bond to a central metal ion
What is the difference between monodentate and bidentate ligands
monodentate - a ligand that donates one pair of lone electrons to the central metal ion
bidentate - a ligand that donates two lone pairs of electrons to the central metal ion
What are the 5 most common monodentate ligands and their charges?
h2o - neutral
Nh3 - neutral
Cl -1
OH -1
CN -1
What are the 2 most common bidentate ligands?
1,2diaminoethane
ethanedioate
What do ligands 1,2diaminoethane and ethanedioate share in common?
the both form two coordinate bonds
What is the shape and bond angle of six-coordinate complexes?
octahedral
90 degrees
What is the shape and bond angle of four-coordinate complexes?
tetrahedral
109.5
define stereoisomers
the same structural formula but different arrangements in space
How is stereoisomerism different in complex ions in comparison to organic chemistry?
In organic chemistry Cis/Trans isomerism requires the presence of a C=C which restricts rotation
No double bond is involved with complex ions, cis and trans isomers are defined by the orientation of ligands
What are optical isomers?
Non-superimposable mirror images of each other
What are optical isomers also known as?
enantiomers
When does optical isomerism occur
In octahedral complexes where there are at least 2 bidentate ligands
what is ligand substitution
When one ligand in a complex ion is replaced by another ligand
Ligand substitution with ammonia
[Cu(H2O)6]2+(aq) + 4NH3(aq) - > [Cu(NH3)4(H2O)2]2+(Aq) + 4H2O(l)
hexa aqua copper(II) ions + ammonia
[Cu(H2O)6]2+(aq) - pale blue
dropwise - Cu(OH)2 - light blue precipitate
excess - tetra di amine di aqua copper (II) - dark blue - precipitate dissolved
Ligand substitution with chloride ions
[Cu(H2O)6]2+(aq) + 4Cl-(Aq) -> [CuCl4]2- + 6H2O(l)
HCl can be used as a source of chloride ions
pale blue -> yellow
In ligand substitution with chloride ions, how come the co-ordination number changes
Cl- ligand is larger in size than the H2O ligand
Therefore takes up more space so fewer Cl ligands fit around the central metal ion
