Transition metals Flashcards
What are d block transition metals
The d-block transition metals are metals with an incomplete d subshell in at least one of their ions.
The filling of d orbitals follows what principal
The filling of the d orbitals follows the aufbau principle, with the exception of chromium and copper atoms.
Why do chromium and copper atoms not follow the aufbau principal
These exceptions are due to the special stability associated with the d subshell being half- filled or completely filled.
What happens to electrons when atoms from the first row of transition elements form ions
When atoms from the first row of the transition elements form ions, it is the 4s electrons that are lost first rather than the 3d electrons.
When is a element said to be in a particular oxidation state
An element is said to be in a particular oxidation state when it has a specific oxidation number.
How many states can a transition metal have in its compounds
A transition metal can have different oxidation states in its compounds.
What colours are compounds of the same transition metal in different oxidation states
Compounds of the same transition metal in different oxidation states may have different colours.
Oxidation
Oxidation can be defined as an increase in oxidation number.
Reduction
Reduction can be considered as a decrease in oxidation number.
What can be used to determine whether ox or red has occurred in transition metals
Changes in oxidation number of transition metal ions can be used to determine whether oxidation or reduction has occurred.
What is the difference in compounds containing Hugh oxidation states compared to low oxidation states
Compounds containing metals in high oxidation states are often oxidising agents, whereas compounds with metals in low oxidation states are often reducing agents.
What are ligands
Ligands may be negative ions or molecules with non-bonding pairs of electrons that they donate to the central metal atom or ion, forming dative covalent bonds.
Ligands can be classified as:
monodentate, bidentate, up to hexadentate.
How can you deduce the ligand classification
It is possible to deduce the ligand classification from a formula or structure of the ligand or complex.
What is the coordination number
The total number of bonds from the ligands to the central transition metal is known as the coordination number.
What happens to d orbitals in a complex of a transition metal
In a complex of a transition metal, the d orbitals are no longer degenerate.
When does splitting of d orbitals to higher and lower energies occur
Splitting of d orbitals to higher and lower energies occurs when the electrons present in approaching ligands cause the electrons in the orbitals lying along the axes to be repelled.
What are strong field ligands
Ligands that cause a large difference in energy between subsets of d orbitals are strong field ligands.
What are weak field ligands
Weak field ligands cause a small energy difference.
What is the spectrochemical series
Ligands can be placed in an order of their ability to split d orbitals. This is called the spectrochemical series.
When is light absorbed
Light is absorbed when electrons in a lower energy d orbital are promoted to a d orbital of higher energy.
What happens if light of one colour is absorbed
If light of one colour is absorbed, then the complementary colour will be observed.
What else can transition metals act as
Transition metals and their compounds can act as catalysts.
What is the state of heterogenous catalysts
Heterogeneous catalysts are in a different state to the reactants.
What state are homogenous catalysts in
Homogeneous catalysts are in the same state as the reactants.
Homogenous catalysts
Homogeneous catalysis can be explained in terms of changing oxidation states with the formation of intermediate complexes.
What does the presence of unpaired d electrons or infilled d orbitals allow
The presence of unpaired d electrons or unfilled d orbitals is thought to allow activated complexes to from. This can provide reaction pathways with lower energies compared to the uncatalysed reaction
Which ions are more stable
Half fill or full filled sub shell stability more stable
Monodentate ligand examples and charges
Chlorido - Cl-
Ammine NH3 - neutral ligand
Aqua OH2 - neutral ligand
Cyanido - CN-
Nitrito - NO2-
What is an explanation of the spectrochemcial series
- changing the ligand of a transition metal changes the repulsion in d electrons /orbitals this changes the level of splitting therefore changing the energy absorbed when d electrons and promoted to higher levels changing the wavelength of light that’s absorbed.
When a complex is colourless /least colourful
No d electrons in the subshell or D electron is full
Naming transition metal complexes
- The formula of the complex ion should be enclosed within square brackets, The metal
Symbol is written first, then the ligands in alphabetical order. Eg. (Fe(NHs)-(OH2412* - The name of the complex ion or molecule consists of two parts written as one word. The ligands are named first and the central metal ion second
- The ligand name is preceded by a prefix showing the number of ligands (di. tri, etc). If the ligand is a negative ion the name of which ends in -ide. the ending changes to o e.g. Chloride, CI becomes chlorido, cyanide, CN becomes cyanido. If the ligand is a negative ion which ends in -ite, the final ‘e’ changes to ‘o’, e.g. nitrite, NO2. changes to nitrito.
4.The metal name is followed by its oxidation state in Roman numerals in brackets. If the complex is an anion (negative ion), ‘ate’ is added to the name of the metal, sometimes the name ending of the metal is dropped. Sometimes the Latin name is used, e.g. ferrate not ironate, cuprate not copperate.
The oxidation number can be determined by the following:
- uncombined elements have an oxidation number of 0
- ions containing single atoms have an oxidation number that is the same as the charge
on the ion - in most of its compounds, oxygen has an oxidation number of −2
- in most of its compounds, hydrogen has an oxidation number of +1
- the sum of all the oxidation numbers of all the atoms in a neutral compound must add
up to zero - the sum of all the oxidation numbers of all the atoms in a polyatomic ion must be equal
to the charge on the ion
