DM.1

Question 1

Why are d-block elements so different to elements from other parts of the periodic table?

Answer 1

They have special electronic configurations and energy levels associated with their electrons, giving them special properties.

Question 2

What would you say about the differences between elements within a group in the d-block compare to other parts of the periodic table?

Answer 2

They are less apparent compare to other parts of the periodic table like group 1 and 2.

Question 3

What would you say about the similarities between elements across a period in the d-block compare to other parts of the periodic table?

Answer 3

There are greater similarties across a period between elements.

Question 4

What is the electron configuration of scandium, Sc, representing core electron configuration with [Ar]?

Answer 4

[Ar]3d1 4s2

Question 5

What is the electron configuration of titanium, Ti, representing core electron configuration with [Ar]?

Answer 5

[Ar]3d2 4s2

Question 6

What is the electron configuration of vanadium, V, representing core electron configuration with [Ar]?

Answer 6

[Ar]3d3 4s2

Question 7

What is the electron configuration of chromiun, Cr, representing core electron configuration with [Ar]?

Answer 7

[Ar] 3d5 4s1

Question 8

What is the electron configuration of manganese, Mn, representing core electron configuration with [Ar]?

Answer 8

[Ar]3d5 4s2

Question 9

What is the electron configuration of iron, Fe, representing core electron configuration with [Ar]?

Answer 9

[Ar]3d6 4s2

Question 10

What is the electron configuration of cobalt, Co, representing core electron configuration with [Ar]?

Answer 10

[Ar]3d7 4s2

Question 11

What is the electron configuration of nickel, Ni, representing core electron configuration with [Ar]?

Answer 11

[Ar]3d8 4s2

Question 12

What is the electron configuration of copper, Cu, representing core electron configuration with [Ar]?

Answer 12

[Ar]3d10 4s1

Question 13

What is the electron configuration of zinc, Zn, representing core electron configuration with [Ar]?

Answer 13

[Ar]3d10 4s2

Question 14

Why are electrons arranged in the way shown in the electronic configuration when the atom is in its ground state?

Answer 14

Because the electronic arrangement would give the lowest total energy, making it more stable.

Question 15

Because electrons repel each other, what kind of orbiting arrangement would give the lowest total energy?

Answer 15

When electrons orbit singly in their orbitals than if they are paired up.

Question 16

Why does chromium’s electron configuration not fit with the predicted pattern of adding one electron to the d orbital everytime?

Answer 16

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.

Question 17

Similarly, why does copper’s electron configuration not fit with the pattern?

Answer 17

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.

Question 18

Which electrons are always lost first when ions of transition metals are formed?

Answer 18

The 4s electrons.

Question 19

What is the definition of a transition metal?

Answer 19

D-block elements that can form one or more stable ions with incompletely filled/partially filled d-orbitals.

Question 20

What is the relationship between d-block elements and transition metals?

Answer 20

All transition metals are d-block elements, but not all d-block elements are transtion metals.

Question 21

Which elements from the first row of d-block elements are not classes as transition metals?

Answer 21

Scandium and zinc.

Question 22

Which columns of the d-block contain elements that are not classed as transtion metals?

Answer 22

The first column and the last column.

Question 23

Why is scandium not classed as a transition metal?

Answer 23

Scandium only forms Sc3+ ions, and the electron configuration of this ion has an empty d-orbital.

Question 24

The Sc3+ ion behaves similarly to which element?

Answer 24

Aluminium

Question 25

Why is zinc not classed as a transition metal?

Answer 25

Zinc only forms Zn2+ ions, and the electron configuration of this ion has a filled 3d orbital.

Question 26

The Zn2+ behaves similarly to which group of elements?

Answer 26

Group 2.

Question 27

What are four signiture properties of transition metals?

Answer 27

1. Variable oxidation states 2. Catalyst activity 3. Coloured compounds 4. Complex formation

Question 28

Why can transition metals exist in a number of oxidation states?

Answer 28

Because there are several stable arrangements of the d electrons and s electrons.

Question 29

What method can be used to analyse the iron content in solution using the ideas of transition metal variable oxidation states?

Answer 29

Redox titration.

Question 30

What oxidising agent is used in the redox titration to find the concentration of iron in a solution?

Answer 30

Manganate(VII) ions, which can be found in potassium manganate(VII) solution.

Question 31

What condition should the redox titration be carried out in and why?

Answer 31

Acidic conditions, it provides the H+ ions needed to reduce the oxidising agent.

Question 32

What colour is manganate(VII) ion?

Answer 32

Purple

Question 33

What is the half equation that shows iron(II) being oxidised?

Answer 33

Fe2+(aq) → Fe3+(aq) +e-

Question 34

What is the half equation that shows manganate(VII) being reduced?

Answer 34

MnO4-(aq) + 8H+(aq) +5e- → Mn2+(aq) + 4H2O(l)

Question 35

Why is manganate(VII) ion a good oxidising agent?

Answer 35

Because the oxidisation state of manganate is +7, the highest oxidising state, and therefore can be very easily reduced.

Question 36

What acid should be used in the redox titration?

Answer 36

Sulfuric acid. Do not use hydrochloric acid, because chloride ions are easily oxdised and chlorine gas can be produced.

Question 37

What would be observed at the end point and what does it imply?

Answer 37

When a pink colour persists in the previously colourless solution, this indicates that mangante(VII) ions are in excess.

Question 38

Desribe the method of the redox titration to find the concentration of iron in a solution?

Answer 38

1. Put the standard MnO4- solution in the burette. 2. Use a volumetric pipette to transfer the solution containing iron to a conical flask. 3. Add excess H2SO4 to the flask. 4. Titrate until a faint pink colour persist due to excess MnO4-. 5. Repeat titration until you get concordant results.

Question 39

Why is an indicator not required for redox titration with MnO4-?

Answer 39

Because MnO4- ions have a purple colour which would be observed.

Question 40

What is another oxidising agent you could use instead of manganate(VII) to find iron concentration?

Answer 40

Dichromate(VI) ion, which has an orange colour.