Periodicity HL

Question 1

What is a transition element

Answer 1

an element with an incomplete d sub-level or can form positive ions with an incomplete d sub-level

Question 2

What element is not actually a transition element and why

Answer 2

Zinc: it has a complete d sub-level as an atom and ion
Sc: it has no d sub-level as an ion

Question 3

What is the electron configuration for Cu

Answer 3

4s1 3d10

Question 4

What is the electron configuration for Cr

Answer 4

4s1 3d5

Question 5

List physical properties of transition metals

Answer 5

• malleable and ductile
• good electrical and heat conductor
• high tensile strength
• high melting + boiling points
• show magnetic properties

Question 6

List chemical properties of transition metals

Answer 6

• variable oxidation states
• formation of complex ions
• coloured compounds
• catalytic behaviour

Question 7

Why do transition metals have variable oxidation states

Answer 7

the 3d and 4s orbitals close in energy which results in a small difference in ionisation energy (there is still a gradual increase in successive ionisation). Transition elements can lose varying number of electrons with the same relative ease

Question 8

What is a complex ion

Answer 8

transition metal ions can form complexes which consist of a central metal ion and ligands

Question 9

What are ligands

Answer 9

molecules or ions with a lone pair of electrons (or more) that form coordinate covalent bonds with a central metal ion

Question 10

Properties/features of ligands

Answer 10

• they have a lone pair of electron
• they can be Lewis bases
• they have a negative charge

Question 11

What is a co-ordination number

Answer 11

the number of co-ordinate bonds

Question 12

Name a couple of common ligands

Answer 12

H2O, OH-, CN-, NH3, Cl-

Question 13

What is a bidentate ligand

Answer 13

• they form 2 co-ordinate bonds with the central atom
• each ligand contains 2 atoms with lone pairs

Question 14

What is a polydentate ligand

Answer 14

• they form more than 2 co-ordinate bonds with the central atom
• each ligand contains more than 2 atoms with lone pairs

Question 15

What is an example of a polydentate ligand

Answer 15

EDTA

Question 16

What are coordination compounds

Answer 16

they are made up of complex ion and counter ions which balance the charge of the complex ion

Question 17

What is a co-ordinate bond

Answer 17

a covalent bond in which both electrons come from the same atom

Question 18

What is a catalyst

Answer 18

a substance that provides an alternative pathway with a lower activation energy

Question 19

What are the 2 types of catalysts

Answer 19

homogenous and heterogeneous

Question 20

Why are transition metals good catalysts

Answer 20

their ability to form variable oxidation states means they can accept electrons easily

Question 21

What is a heterogeneous catalyst

Answer 21

a catalyst that is in the same phase (physical state) as its reactants

Question 22

What is a homogenous catalyst

Answer 22

a catalyst that is in a different phase (physical state) from its reactants

Question 23

List examples of heterogeneous catalysts

Answer 23

• Fe (Haber process)
• Ni (hydrogenation of margarine)
• Pd & Pt (catalytic converter)
• V2O5 (Contact process)
• MnO2 (decomposition of H2O2)

Question 24

List examples of homogenous catalysts

Answer 24

• Fe (heamoglobin)
• Co (vitamin B12)

Question 25

What does paramagnetic mean

Answer 25

substances that have unpaired electrons

Question 26

What does diamagnetic mean

Answer 26

substances that have no unpaired electrons

Question 27

What does ferromagnetic mean

Answer 27

only occurs with Fe, Co, Ni: the attraction to a magnetic field is so much stronger in these metals because a large number of unpaired electrons line up in regions called domains

Question 28

Why do transition metal compounds appear coloured

Answer 28

they absorb energy corresponding to certain parts of the electromagnetic spectrum and the complementary colour will be transmitted (ex: orange light being absorbed corresponds to blue light being transmitted)

Question 29

Describe the Crytsal Field Theory

Answer 29

- As the ligand approaches the metal to form a complex ion the lone pairs of electrons on the ligand will repel the d orbital causing the five d orbitals to split: 3 to lower energy and two to higher energy - The energy gap between the two levels correspond to the wavelength of visible light - Electrons can transition from the lower to a higher set of d orbitals by absorbing certain wavelengths of light.

Question 30

What are the factors that affect the colour of transition metal compound

Answer 30

- the size and types of ligands - the nuclear charge and identity of the metal ion - the oxidation state of the metal - the shape of the complex

Question 31

How does the nuclear charge affect the colour of the transition metal compound

Answer 31

The greater the charge density; the more strongly the ligand interacts with the metal ion causing greater splitting of the d-orbitals. As a result, a different colour of light is absorbed by the complex solution and a different complementary colour is observed.

Question 32

How does the oxidation state affect the colour of the transition metal compound

Answer 32

When the same metal is in a higher oxidation state that will also create a stronger interaction with the ligands

Question 33

The spectrochemical series

Answer 33

the higher up the ligan on the spectrochemical series, the greater their ability to separate the d-orbitals, the shorter the waevelegnth absorbed