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C - Inorganic > Unit 2: Section 4 - Transition Metals > Flashcards

Unit 2: Section 4 - Transition Metals Flashcards

1
Q

Where are transition metals found in the periodic table?

A

The d block

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2
Q

What is the definition of a transition metal?

A

A transition metal is a metal that can form one or more stable ions with a partially filled d sub-shell.

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3
Q

Which period 4 d block elements are not transition metals? Why?

A

Scandium - it only forms one ion (Sc3+), which has an empty d sub-shell.
Zinc - it only forms one ion (Zn2+), which has a full d sub-shell.

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4
Q

Which period 4 transition metals do not follow the definition of a transition metal? In what way?

A

Chromium and copper, as they only half fill the 4s sub-level before filling the 3d sub-level.

e.g. Chromium is [Ar] 3d5, 4s1, while manganese, which is right after it is [Ar] 4s2, 3d5

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5
Q

When positive ions are formed, which electrons are removed first?

A

s electrons

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6
Q

Do transition metals form positive or negative ions?

A

Positive

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7
Q

What are the physical properties of transition metals? (3)

A

They all have high density
They all have high melting and boiling points
Their ionic radii are more or less the same

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8
Q

What are the special chemical properties of transition metals? (4)

A

They can form complex ions
They form coloured ions
They’re good catalysts
They can exist in variable oxidation states

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9
Q

Why do elements show variable oxidation states?

A

The energy levels of the 4s and the 3D sub-shells are very close to each other, therefore different numbers of electrons can be gained or lost using fairly similar amounts of energy.

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10
Q

What is the definition of a complex ion?

A

A metal ion surrounded by co-ordinately bonded ligands.

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11
Q

What is a co-ordinate bond?

A

A covalent bond in which both electrons in the shared pair come from the same atom

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12
Q

What is a ligand?

A

An atom, ion or molecule that donates a pair of electrons to a central transition metal ion.

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13
Q

What is the coordination number?

A

The number of coordinate bonds that are formed with the central metal ion.

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14
Q

6 co-ordinate bonds mean an ______ shape, with __ bond angles

A

Octahedral, 90 degrees

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15
Q

4 co-ordinate bonds mean a ______ or ______ shape, with bond angles of __ and __.

A

Tetrahedral, 109.5 degrees

Square Planar, 90 degrees

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16
Q

2 co-ordinate bonds mean a ______ shape, with a bond angle of __.

A

Linear, 180 degrees

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17
Q

What is the total oxidation state?

A

The overall charge on the complex ion

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18
Q

What is the formula to work out the oxidation state of the metal ion?

A

the oxidation state of the metal ion =

total oxidation state - sum of oxidation states of ligands

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19
Q

A ligand must have at least one _________________.

A

Lone pair of electrons

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20
Q

What are monodentate ligands?

A

Ligands that can only form one co-ordinate bond.

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21
Q

What are multidentate ligands?

A

Ligands that can form more than one co-ordinate bond.

22
Q

What are bidentate ligands?

A

Multidentate ligands that can form two co-ordinate bonds.

23
Q

What is is haemoglobin?

A

A protein found in the blood which helps to transport oxygen around the body.

24
Q

Haemoglobin contains ___ ions, which are ___-coordinated - ___ lone pairs are donated to form ___ co-ordinated bonds in an _________ structure.

A 
Fe2+ 
Hexa
Six
Six
Octahedral
25
Q

____ of the co-ordinate bonds come from a ______________, (consisting of _________________ atoms from the same molecule around the centre to form a circle. The is called the _____.The other ___ co-ordinate come from a protein called ______ and either an ______ or a ______ molecule so the complex can transport oxygen to where it’s needed.

A 
Four 
Single multidentate ligand
Four nitrogen atoms
Haem 
Two
Globin
Oxygen
Water
26
Q

What happens to haemoglobin in high oxygen concentration?

A

An oxygen molecule substitutes the water ligand and bonds co-ordinately to the Fe2+ to form oxyhaemoglobin, which is carried around the body in the blood.

27
Q

What happens to haemoglobin in low oxygen concentration?

A

The oxygen molecule in oxyhaemoglobin is exchanged for a water molecule. The haemoglobin then returns to the blood.

28
Q

What happens to haemoglobin if carbon monoxide is introduced into the body?

A

The haemoglobin swaps its water ligand for a carbon monoxide ligand, forming carboxyhaemoglobin. This means oxygen can’t be transported anymore as carbon monoxide ligands are strong ligands that can’t easily be substituted by water or oxygen ligands.

29
Q

What is optical isomerism?

A

Where an ion can exist in two forms that are non-superimbosable mirror images.

30
Q

When does optical isomerism occur in complex ions?

A

When three bidentate ligands co-ordinately bond with a central metal ion to create an octahedral complex.

31
Q

What is cis-trans isomerism?

A

A special type of E/Z isomerism.

32
Q

When does cis-trans isomerism occur in complex ions?

A

In octahedral and square planar complexes.

33
Q

Describe how complex ions show cis-trans isomerism.

A

In octahedral complexes: If you have four monodentate ligands of one type and two monodentate ligands of another type, with the two monodentate ligands opposite each other this is a trans isomer. If they are next to eachother this is a cis isomer.

In square planar complexes: If it has two pairs of ligands they are likely to show cis-trans isomerism. When the two pairs are opposite each other it is a trans isomer and if they are next to each other it is a cis isomer.

34
Q

What is the formula to find the energy gap?

A

hv - hc / λ

h = Planck's constant (6.63 x 10^-34 Js)
v = frequency of light absorbed (hertz/Hz)
c = the speed of light (3 x 10^8 ms^-1)
λ = wavelength of light absorbed (m)
35
Q

What is the energy gap?

A

The energy absorbed when the electrons jump up from the ground state to an excited state.

36
Q

What happens when visible light hits a transition metal ion?

A

Some frequencies of light are absorbed and other frequencies are transmitted or reflected. The frequencies absorbed depends on the size of the energy gap.

37
Q

What is it that makes the transition metal ions coloured?

A

The transmitted or reflected frequencies of light combine to make the complement of the colour of the absorbed frequencies of light.

38
Q

What can alter the colour of a complex? (3)

A

Anything which affects the size of the energy gap:

  1. Changes in oxidation state
  2. Changes in co-ordination number - which always includes and change in ligand too.
  3. Changes in ligand - this can cause a change even if the oxidation state and co-ordination number remain the same.
39
Q

Describe and explain why transition metal ions have a differently configured 3d sub-shell to other atoms.

A

Ligands split the 3d orbitals into two different energy levels, but in regular atoms, the 3d orbitals all have the same energy. This happens because the ligands cause some of the orbitals to gain energy, while some of the others do not.

40
Q

Where do you find most electrons in the 3d sub-shells of transition metal ions?

A

In the lower orbitals/the ground state.

41
Q

How do electrons move within the 3d sub-shells?

A

They need energy equal to the energy gap to jump up to the excited state, which usually comes from visible light.

42
Q

Define ligand substitution.

A

One ligand is swapped for another

43
Q

What are two basic rules for ligand substitution, relating size, shape and co-ordination number?

A
  1. If the ligands are of similar shape and the same charge, then the co-ordination number of the complex doesn’t change, and neither does the shape.
  2. If the ligands are different sizes, there’s a change of co-ordination number and a change of shape.
44
Q

Can ligand substitution reactions be reversed?

A

They can be easily reversed unless the new complex ion is more stable. This makes it much more difficult.

45
Q

Which type of ligand forms more stable complexes?

A

Multidentate

46
Q

What happens to co-ordinate bonds when a ligand exchange reaction occurs?

A

They are broken and formed

47
Q

What is the enthalpy change in a ligand exchange reaction? Why?

A

The enthalpy change is usually very small. This is because the strength of the co-ordinate bonds being broken is often similar to the strength of the co-ordinate bonds being made.

48
Q

Why is it more difficult to reverse a ligand substitution reaction which makes a more stable complex?

A

Equilibrium lies very far to the right after the reaction takes place as reversing the reaction would cause a decrease in entropy.

49
Q

What causes the equilibrium change that occurs when a more stable complex is formed via a ligand exchange reaction?

A

A highly positive entropy

50
Q

What is the chelate effect?

A

When monodentate ligands are substituted for multidentate or bidentate ligands, the number of particles in the solution increases, and the more particles the greater the entropy. Reactions that result in an increase in entropy are more likely to occur.

51
Q

What reaction occurs when you switch between oxidation states?

A

Redox reactions

C - Inorganic (4 decks)

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