Developing Metals

Question 1

What are transition metals?

Answer 1

d-block elements that form 1 or more stable ions with incompletely filled d-orbitals

Question 2

What are the 2 main reasons why d-block elements have many features in common?

Answer 2

Have essentially the same outer electronic arrangement - nearly all have 4s²

Unlike other elemental groups don’t differ by complete electronic group but only by 1 more e^- in incomplete inner 3d sub-shell

Question 3

What is the convention for writing out the order of electronic sub-shells?

Answer 3

Principle electron shells kept together

Means [Ar]3s²3p⁶3d¹⁰4s² even though 4s filled before 3d

(as is at a lower energy level)

Question 4

What is the electronic configuration of an Iron(II) ion?

Answer 4

[Ar]3s²3p⁶3d⁶

Question 5

What is the electronic configuration of an Iron(III) ion?

Answer 5

[Ar]3s²3p⁶3d⁵

Question 6

What is the electronic configuaration of a Copper(I) ion?

Answer 6

[Ar]3s²3p⁶3d¹⁰

Question 7

What is the electronic configuration of a Copper(II) ion?

Answer 7

[Ar]3s²3p⁶3d⁹

Question 8

What colour is an aqueous Iron(II) ion?

Answer 8

Green

Question 9

What colour is an aqueous Iron(III) ion?

Answer 9

Orange/Brown

Question 10

What colour is an aqueous Copper(I) ion?

Answer 10

N/A

Doesn’t form aquesous ions

(Due to disproportionation reaction - Cu + Cu²⁺ always formed instead)

Question 11

What colour is an aqueous Copper(II) ion?

Answer 11

Blue

Question 12

Why do Cr and Cu have odd electronic configurations?

Answer 12

In the ground state, e^- are arranged to give the lowest total energy

In period 4, the energies of 3d + 4s orbials are very close together therefore causing odd configuartions

Question 13

What is the electronic configuration of Cr and why is this?

Answer 13

[Ar]3s²3p⁶3d⁵4s¹

NOT 3d⁴4s²

1e^- in each 3d orbital + the 4s orbital

Question 14

What is the electronic configuration of Cu and why is this?

Answer 14

[Ar]3s²3p⁶3d¹⁰4s¹

NOT 3d⁹4s²

2e^- in 4s would be higher energy than filling 3d subshell

Question 15

What test can be used to identify Fe²⁺, Fe³⁺, and Cu²⁺ ions in solution and why?

Answer 15

Using NaOH_(aq) as they all form precipitates

Question 16

What is formed when NaOH_(aq) is added to an Fe²⁺ solution?

Give the equation and colour of the precipitate

Answer 16

Iron(II) hydroxide - green precipitate

Fe²⁺_(aq) + 2OH^-_(aq) → Fe(OH)_2(s)

Question 17

What is formed when NaOH_(aq) is added to an Fe³⁺ solution?

Give the equation and colour of the precipitate

Answer 17

Iron(III) hydroxide - brown precipitate

Fe³⁺_(aq) + 2OH^-_(aq) → Fe(OH)_2(s)

Question 18

What is formed when NaOH_(aq) is added to an Cu²⁺ solution?

Give the equation and colour of the precipitate

Answer 18

Copper(II) hydroxide - pale blue precipitate

Cu²⁺_(aq) + 2OH^-_(aq) → Fe(OH)_2(s)

Question 19

What reactions occur is ammonia is added to aqueous Fe²⁺, Fe³⁺, or Cu²⁺ ions?

Why?

Answer 19

The same reactions as when NaOH_(aq) added - hydroxide precipitates formed

Because ammonia is also a source of OH^- ions

Question 20

What reaction occurs when excess ammonia is added to precipitate of Cu(OH)₂?

Answer 20

Pale blue Cu(OH)₂ precipitate dissolves to form deep blue solution of copper ammonia complex [Cu(NH₃)(H₂O)₂]²⁺_(aq)

Question 21

How is the reaction of Cu²⁺ with excess ammonia different to those of Fe²⁺ and Fe³⁺?

Answer 21

Fe(OH)₂ and Fe(OH)₃ don’t form complexes with ammonia

Question 22

What is a complex?

Answer 22

A central metal atom surrounded by negative ions/neutral molecules posessing a long pair (ligands)

Question 23

What is a ligand?

Answer 23

A negatively charged/neutral molecular with a lone pair of electrons, surrounding a transition metal/ion.

Attached to metal by dative covalent bonds

Question 24

Define co-ordination number

Answer 24

The number of bonds from the central metal atom/ion (in a compex) to ligands.

NOT necessarily the number of ligands! (e.g. is bi/polydentate)

Question 25

What is a complex ion?

Answer 25

Transition metal surrounded by a number of ligands

Question 26

What is a monodentate ligand?

Answer 26

Ligand that attaches to a transition metal through 1 atom only

Question 27

What is a bidentate ligand?

Answer 27

A ligand with 2 long pairs/negative charges that forms 2 bonds to a metal atom/ion

Question 28

What is a polydentate ligand?

Answer 28

A ligand that forms several bonds to a metal atom/ion and has several lone pairs/areas of negative charge

Question 29

What is a chelate ring?

Answer 29

A many-membered ring that forms when a bi/polydentate ligand bonds to a metal.

Question 30

What type of ligand is an ethanedioate ion?

What is its chemical formula?

Answer 30

A bidentate ligand

^-OOC-COO^-

Question 31

What is a ligand substitution reaction?

Answer 31

When one ligand replaces another in a complex

Question 32

What is necessary for a ligand substitution reaction to occur?

What can be used to determine whether it will occur or not?

Answer 32

Will only occur if the new complex is more stable than the old, therefore the stability of the complex depends on its ligands

If the K_stab value is higher for the new ligand then substitution will occur

Question 33

What shape and colour is a [Cu(H₂O)₆]²⁺ complex?

Answer 33

Blue

Octahedral

Question 34

What are the two possible ligand substitution reactions for a [Cu(H2O)6]2+ ion?

What colour + shape are the complexes formed?

Answer 34

[CuCl₄] Tetrahedral + Yellow

[Cu(NH₃)₄(H₂O)₂]²⁺ Octahedral + Deep blue/violet

Question 35

What are the four possible shapes a compex ion can be?

Answer 35

Linear

Square planar

Tetrahedral

Octahedral

Question 36

What does a linear complex ion look like + what are its co-ordination number and bond angles?

Answer 36

Co-ordination no = 2

Bond angles = 180º

Question 37

What does a square planar complex ion look like + what are its co-ordination number and bond angles?

Answer 37

Co-ordination no = 4

Bond angles = 90º

Question 38

What does a tetrahedral complex ion look like + what are its co-ordination number and bond angles?

Answer 38

Co-ordination number = 4

Bond angles = 109.5º

Question 39

What does a octahredral complex ion look like + what are its co-ordination number and bond angles?

Answer 39

Co-ordination no = 6

Bond angles = 90º

Question 40

What does the presence of ligands cause the d sub-shell to do?

Answer 40

Split into higher + lower energy levels

Question 41

Why are d-block complex ions coloured?

Answer 41

The presence of ligands causes the d sub-shell to split into higher + lower energy levels

When visible light is absorbed, e^- can be excited to a higher energy level.

The frequency of light absorbed is proportional to the gap between energy levels -ΔE = hv

The complimentary colour is transmitted and is the colour we observe

Question 42

What factors affect the gap between energy levels of ligands?

In other words, why are metal complexes different colours?

Answer 42

Number of e^- present in metal (i.e what metal/oxidation state)

Arrangement of ligands around ion as this affects splitting of d-shell

Nature of ligand - differone ones have different effects on relative energies of d-orbitals in a particular ion

Question 43

What technique can be used to find the concentration of a coloured solution?

Why?

Answer 43

Colorimetry

Because absorbance is proportional to concentration

Therefore greater absorbtion = greater concentration