DM.1 Flashcards
Introduction to transition metals and their oxidation states
Why are d-block elements so different to elements from other parts of the periodic table?
They have special electronic configurations and energy levels associated with their electrons, giving them special properties.
What would you say about the differences between elements within a group in the d-block compare to other parts of the periodic table?
They are less apparent compare to other parts of the periodic table like group 1 and 2.
What would you say about the similarities between elements across a period in the d-block compare to other parts of the periodic table?
There are greater similarties across a period between elements.
What is the electron configuration of scandium, Sc, representing core electron configuration with [Ar]?
[Ar]3d1 4s2
What is the electron configuration of titanium, Ti, representing core electron configuration with [Ar]?
[Ar]3d2 4s2
What is the electron configuration of vanadium, V, representing core electron configuration with [Ar]?
[Ar]3d3 4s2
What is the electron configuration of chromiun, Cr, representing core electron configuration with [Ar]?
[Ar] 3d5 4s1
What is the electron configuration of manganese, Mn, representing core electron configuration with [Ar]?
[Ar]3d5 4s2
What is the electron configuration of iron, Fe, representing core electron configuration with [Ar]?
[Ar]3d6 4s2
What is the electron configuration of cobalt, Co, representing core electron configuration with [Ar]?
[Ar]3d7 4s2
What is the electron configuration of nickel, Ni, representing core electron configuration with [Ar]?
[Ar]3d8 4s2
What is the electron configuration of copper, Cu, representing core electron configuration with [Ar]?
[Ar]3d10 4s1
What is the electron configuration of zinc, Zn, representing core electron configuration with [Ar]?
[Ar]3d10 4s2
Why are electrons arranged in the way shown in the electronic configuration when the atom is in its ground state?
Because the electronic arrangement would give the lowest total energy, making it more stable.
Because electrons repel each other, what kind of orbiting arrangement would give the lowest total energy?
When electrons orbit singly in their orbitals than if they are paired up.
Why does chromium’s electron configuration not fit with the predicted pattern of adding one electron to the d orbital everytime?
This is because having the six electrons all singly in orbitals give a lower energy arrangement. By moving one electron from the s orbital to the d orbital avoids having pairs of electrons in the same orbital.
Similarly, why does copper’s electron configuration not fit with the pattern?
The 3d orbitals are at lower energy than the 4s orbitals therefore the lowest total energy would be when all the electron pairs are in the d orbitals rather than having one in the s orbital.
Which electrons are always lost first when ions of transition metals are formed?
The 4s electrons.
What is the definition of a transition metal?
D-block elements that can form one or more stable ions with incompletely filled/partially filled d-orbitals.
What is the relationship between d-block elements and transition metals?
All transition metals are d-block elements, but not all d-block elements are transtion metals.
Which elements from the first row of d-block elements are not classes as transition metals?
Scandium and zinc.
Which columns of the d-block contain elements that are not classed as transtion metals?
The first column and the last column.
Why is scandium not classed as a transition metal?
Scandium only forms Sc3+ ions, and the electron configuration of this ion has an empty d-orbital.
The Sc3+ ion behaves similarly to which element?
Aluminium
Why is zinc not classed as a transition metal?
Zinc only forms Zn2+ ions, and the electron configuration of this ion has a filled 3d orbital.
The Zn2+ behaves similarly to which group of elements?
Group 2.
What are four signiture properties of transition metals?
- Variable oxidation states
- Catalyst activity
- Coloured compounds
- Complex formation
Why can transition metals exist in a number of oxidation states?
Because there are several stable arrangements of the d electrons and s electrons.
What method can be used to analyse the iron content in solution using the ideas of transition metal variable oxidation states?
Redox titration.
What oxidising agent is used in the redox titration to find the concentration of iron in a solution?
Manganate(VII) ions, which can be found in potassium manganate(VII) solution.
What condition should the redox titration be carried out in and why?
Acidic conditions, it provides the H+ ions needed to reduce the oxidising agent.
What colour is manganate(VII) ion?
Purple
What is the half equation that shows iron(II) being oxidised?
Fe2+(aq) → Fe3+(aq) +e-
What is the half equation that shows manganate(VII) being reduced?
MnO4-(aq) + 8H+(aq) +5e- → Mn2+(aq) + 4H2O(l)
Why is manganate(VII) ion a good oxidising agent?
Because the oxidisation state of manganate is +7, the highest oxidising state, and therefore can be very easily reduced.
What acid should be used in the redox titration?
Sulfuric acid. Do not use hydrochloric acid, because chloride ions are easily oxdised and chlorine gas can be produced.
What would be observed at the end point and what does it imply?
When a pink colour persists in the previously colourless solution, this indicates that mangante(VII) ions are in excess.
Desribe the method of the redox titration to find the concentration of iron in a solution?
- Put the standard MnO4- solution in the burette.
- Use a volumetric pipette to transfer the solution containing iron to a conical flask.
- Add excess H2SO4 to the flask.
- Titrate until a faint pink colour persist due to excess MnO4-.
- Repeat titration until you get concordant results.
Why is an indicator not required for redox titration with MnO4-?
Because MnO4- ions have a purple colour which would be observed.
What is another oxidising agent you could use instead of manganate(VII) to find iron concentration?
Dichromate(VI) ion, which has an orange colour.
