Chapter 24 Transition elements

Question 1

What sub-shell is at the highest energy level for transition metals ?

Answer 1

• The d-block elements are found between groups 2 and 13 and have a 3D sub-shell as the highest energy level

Question 2

What is the rule when forming d-block ions/atoms ?

Answer 2

• when forming an ion, lose their 4s electrons before losing any 3d electrons
• when forming an atom 4s fill before 3d

Question 3

What are the physical properties of transition elements ?

Answer 3

• High melting points
• shiny
• Conduct electricity and heat

Question 4

What are some exceptions with D-block atoms ?

Answer 4

• For Cr and Cu a 4s electrons is promoted to half-fill or fully fill the 3d Sub-shell
• this is because it is more energetically favourable

Question 5

What are exceptions of D-block ions ?

defintion of transition element asw

Answer 5

• although in the d-block, Scandium and Zinc do not fall into the definition of a transition element - since neither forms an ion with a partially filled d-orbital
• Scandium only forms +3 ion and zinc only forms a +2 ion

Question 6

What is the pattern of variable oxidation states for transition elements ?

Answer 6

• the number of oxidation states increases across the transition elements series to manganese then decreases

Question 7

What are some common transition element heterogenous catalyst ?

Answer 7

• Hager process - Iron catalyst
• Contact process - Vanadium (V) oxide
• Hydrogenation - nickel catalyst
• Decomposition of hydrogen peroxide - Manganese (IV) oxide catalyst

Question 8

What is a complex ion ?

Answer 8

• Complex ions form when a metal ion is centrally bonded to one or more molecules or negative ions, known as ligands
• Ligands donate a pair of electrons to form a dative bond with the central metal ion
• a coordinate number indicates the number of dative bonds made

Question 9

How do you represent complex ions ?

Answer 9

• Cr3+ is the central metal ion - water acts as a ligand with each molecule donating a lone pair of electrons from the oxygen to the central metal atom to form a coordinate bond
• coordinate number indicates = 6

Question 10

What are the different types of ligands ?

Answer 10

• some ligand have no charge and some do
  2 types of ligands:
  1. Monodentate - donate 1 pair of electrons to central metal ion. E.g Water, ammonia, chloride, cyanide
  2. Bidentate - donate 2 pairs of electrons to central metal ion (2 coordinate bonds)

Question 11

What are the shapes of complex ions ?

Answer 11

• most common coordinate numbers are 6 and 4
• 6-coordinate complexes have octahedral shapes and 90 degree bond angle
• 4-coordinate complexes can have:
  1. tetrahedral shapes 109.5 degree bond angle
  2. Square-planar 90 degree bond angle

Question 12

What is a complex ion example ?

Answer 12

Question 13

What does the colour of complex ions depends on ?

Answer 13

• it depends on the colour of the central atom

Question 14

When do complex ions form Cis-Trans isomerism ?

Answer 14

They can display Cis-Trans isomerism if it contains 2 different monodentate ligands

Question 15

Square planar isomerism example

Answer 15

Question 16

Octahedral monodentate isomerism example

Answer 16

Needs 2 different monodentate ligands with 2 of one ligand and 4 of another ligand

Question 17

Octahedral bidentate isomerism example ?

Answer 17

contain 2 bidentate ligands and 2 monodentate ligands

Question 18

What happens when there is cis isomers in octahedral complexes ?

Answer 18

• Complexes containing monodentate bidentate ligands will display optical isomers (enantiomers)
• only in octahedral complexes
• also occurs in complexes with only bidentate ligands

Question 19

What is Cis-platin ?

Answer 19

• Cis platin was found to bind to DNA and stop cell replication in bacteria
• whereas Trans-platin had no effect as the chlorines can’t bind
• same happens with cancerous cells, making it an effective anti-cancer drugs, however it can attack other cells and cause side effects

Question 20

what is a ligand substitiution reaction ?

Answer 20

• occurs when ligand in a complex ion is replaced with another ligand

Question 21

how does the Cu2+ ion work with ammonia ?

Answer 21

• with the addition of ammonia 4 water ligands are substituted for 4 ammonia ligands
  1. the formation of pale blue precipitate Cu(OH)₂
  2. the precipitate dissolves in excess ammonia to form a **dark blue solution of [Cu(NH₃)₄(H₂O)₂]2+ **

Question 22

how does the Cu2+ ion work with cloride ?

Answer 22

• with the addition of chloride ions (from concentrated HCl) all water ligands are substituted for 4 chloride ligands
• chloride ions are larger than H₂O so less fit around the Cu2+
• Yellow tetrahedral [CuCl₄]2- complex ion forms
• an intermediate solution can form and is green due to equal ammount of complex ions (yellow + blue)

Question 23

how does the Cr3+ ion work with cloride ?

Answer 23

• [Cr(H₂O)₆]3+ is pale purple
• when chormium (III) sulfate dissolves in water a green solution is formed
• with the addition of ammonia all water ligands are substituted for ammonia ligands in 2 steps
  1. a grey-green precipitate of Cr(OH)₃ forms
  2. excess ammonia dissolves precipitate to form dark purple complex ion [Cr(NH₃)₆]3+

Question 24

what are the practical observations of colour for the reactions ?

Answer 24

Question 25

how does **Haemoglobin work**

Answer 25

* Haemoglobin contains 4 protein chains help together by weak intermolecular forces * each chais contains a **Haem group, with a central Fe2+ ion, which can bind to O₂** * oxygen molecules carried by Oxyhaemoglobin can be removed again by substituting water back * however CO can bind to Fe2+ to form, **carboxyhaemoglobin - this bond is much stronger than O₂ and so can't be removed** * this is why CO is toxic and can reduce O₂ blood levels

Question 26

what are the **insoluable precipitation reactions with NaOH** ?

Answer 26

Question 27

what are the **insoluable precipitation reactions with NaOH** ?

Answer 27

Question 28

**transition metal ion reaction summary** | with excess NaOH and NH₃

Answer 28

Question 29

how does **the oxidation of Fe2+ to Fe3+ work** ?

Answer 29

* MnO₄- oxidises Fe2+ as E is **smaller for iron (+1.33V and +0.77V respectively), making iron less likely to gain electrons, so shifting the equilibrium position left** * MnO₄- is reduced and Fe2+ is oxidised

Question 30

how does **the reduction of Fe2+ to Fe3+ work** ?

Answer 30

* I- reduces Fe3+ as **E is larger for iron (+0.54V and +0.77V respectivley) making iron more likely to gain electrons shifting equilibrium to the right**

Question 31

what are the **chromium reduction reactions** ?

Answer 31

Question 32

what are the **chromium oxidation reactions** ?

Answer 32

Question 33

what is the **copper reduction reaction** ?

Answer 33

Question 34

example of **disproportionation of Cu+ ions** ?

Answer 34