Topic 13 Periodicity HL
13.1 Introduction to transition elements
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Essential idea: The transition elements have characteristic properties; these properties are related to their all having incomplete d sub-levels.
Understandings: Zn is not considered to be a transition element as it does not form ions with incomplete d-orbitals. Transition elements have variable oxidation states, form complex ions with ligands, have coloured compounds, and display catalytic and magnetic properties. |
13.1 Complex ions
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Applications and skills:
Explanation of the nature of the coordinate bond within a complex ion. |
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Understandings:
Transition elements have variable oxidation states, form complex ions with ligands, have coloured compounds, and display catalytic and magnetic properties. Essential idea: The transition elements have characteristic properties; these properties are related to their all having incomplete d sub-levels. |
13.1 Ligands
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Understandings:
Ligands are species with lone pairs of electrons that form coordinate covalent bonds to central metal ions. |
13.1 Deduce the charge and oxidation state of a central metal ion
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Applications and skills:
Deduction of the total charge given the formula of the ion and ligands present. Please note that the charge on the central metal ion is the same as the oxidation state, but it is written differently. If the oxidation state is +3, the charge on the metal ion is 3+. |
13.1 Variable oxidation states of the transition elements
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Understandings:
Transition elements show an oxidation state of +2 when the s-electrons are removed. Applications and skills: Explanation of the ability of transition metals to form variable oxidation states from successive ionization energies. |
13.1 Magnetic properties of the transition elements
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Applications and skills:
Explanation of the magnetic properties in transition metals in terms of unpaired electrons. |
13.2 Colour of complex ions
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Understandings:
The d sub-level splits into two sets of orbitals of different energy in a complex ion. Complexes of d-block elements are coloured, as light is absorbed when an electron is excited between the d-orbitals. The colour absorbed is complementary to the colour observed. Guidance: Students are not expected to know the different splitting patterns and their relation to the coordination number. Only the splitting of the 3-d orbitals in an octahedral crystal field is required. |
13.2 Factors that affect the colour of complex ions
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Applications and skills:
Explanation of the effect of the identity of the metal ion, the oxidation number of the metal and the identity of the ligand on the colour of transition metal ion complexes. |
13.2 The Spectrochemical series
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Applications and skills:
Explanation of the effect of different ligands on the splitting of the d-orbitals in transition metal complexes and colour observed using the spectrochemical series. Guidance: The spectrochemical series is given in the data booklet in section 15. |