Q. What is a transition element?
A d-block element that can form one or more stable ions with an incomplete d-subshell.
Q. Describe and explain how the melting points of transition metals are different to those of typical s-block metals, such as calcium.
Transition metals have higher melting points than typical s-block metals, as they have extra 3d electrons, which increase the strength of the metallic bonding, meaning more energy is required to overcome these bonds when melting the metal.
Q. Describe how the densities of transition metals are different to those of a typical s-block metal, such as calcium.
Transition metals have greater densities than s-block metals.
Q. Explain why the densities of transition metals are greater than those of s-block metals, such as calcium.
Nuclear charge increases across the period while electron shielding remains the same, causing the outer shell electrons to be drawn inwards, decreasing the atomic radius. The densities of transition metals are greater than those of s-block metals because the atoms are smaller, so they can pack more closely together, and atomic mass increases across the period.
Q. Why are transition elements used as catalysts?
Transition elements are stable in variable oxidation states, meaning they can take electrons from other molecules.
Q. Why do transition metals have variable oxidation states?
Electrons in the 4s and 3d orbitals have very similar energies. A relatively similar amount of energy is required to gain a different number of electrons.
Q. What is a ligand?
A species that has a lone pair of electrons that forms a dative covalent bond with a central metal atom.
Monodentate ligands form one dative bond, bidentate ligands form two dative bonds, and polydentate ligands form more than two dative bonds.
Q. What is a complex ion?
A molecule containing a central metal ion surrounded by one or more ligands
Q. What is ligand substitution?
A reaction in which one ligand in a complex ion is replaced by another.
Q. What is meant by coordination number?
The number of coordinate bonds formed between the ligands and the central metal atom.
Q. What are degenerate orbitals?
Orbitals with the same energy level.
Q. How are degenerate d-orbitals split into 2 energy levels in octahedral complexes?
The electrons from the ligand repel the d-orbital electrons of the transition metal, which raises the energy of the d orbitals. As a result, the d orbitals are split into two groups: one group has slightly higher energy than the other. The higher-energy group contains two d orbitals, while the lower-energy group also contains two d orbitals.
Q. How are degenerate d-orbitals split into 2 energy levels in tetrahedral complexes?
Ligand electrons repel the d-orbital electrons of the transition metal, which raises the energy levels of the d orbitals. These orbitals are divided into two groups: one group consists of 3 d orbitals with slightly higher energy, while the other group contains 2 d orbitals with lower energy. This arrangement is the opposite of what occurs in octahedral complexes.
Q. How does the quantity of energy absorbed due to the split d orbitals correspond with the colour of the transition metal ion complex?
When white light is passed through the complex, some energy is absorbed and used to raise an electron from the lower d orbital energy level to the higher d orbital energy level. The equivalent wavelength for this quantity of energy is the wavelength of light that is absorbed. The transition metal will be seen as a complementary colour to the colour that was absorbed.
Q. What factors affect the colour of transition metal ion complexes?
- Nature of ligand
- Oxidation state of the metal
- Coordination number of the transition metal ion.
Q. How does the nature of the ligand affect the transition metal ion complex colour?
When ligands create a strong electric field, there will be a larger gap between the d-orbitals. This results in more energy being absorbed, which corresponds to a smaller wavelength of light. If the light absorbed is from the red end of the spectrum, the observed colour will shift away from the red end. Conversely, when ligands produce a weak electric field, there will be a smaller gap between the d-orbitals.
Q. How does the oxidation state of the metal affect the colour of the transition metal ion complex?
As the oxidation state of the metal increases, the amount of d-orbital splitting increases. Therefore affects the amount of energy absorbed and hence the corresponding wavelength of light.
Q. How does the coordination of the ion affect the colour of the transition metal on complex?
For an octahedral molecule, splitting is greater than in a tetrahedral molecule. Greater splitting leads to more energy being absorbed, which in turn means the wavelength of light is smaller.
Q. What does Cisplatin do? (Cisplatin is used as an anti-cancer drug.)
Cisplatin binds to DNA, preventing cells from replicating, leading to cell death (apoptosis) and preventing uncontrolled cell division.
Q. What is Kstab?
The equilibrium constant for the formation of a complex ion from its constituent molecules in a solvent.
Q. What does it mean if the Kstab value is large?
The larger the stability constant, the greater the stability of the complex ion.
Q. Describe ligand exchange in terms of a competing equilibrium.
When there are 2 competing equilibria in a ligand exchange reaction, the reaction that forms the most stable complex will be prioritised. This will be the equilibrium with the greatest Kstab value.
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