Transition metals Flashcards
(74 cards)
1
Q
Define transition metals
A
Metals that can form 1/more stable ions w/ partially filled d sub-shells
2
Q
What causes the special chemical properties of T-metals?
A
Incomplete d sub-shell
3
Q
Why is scandium not a t-metal?
A
- Only forms 1 ion: Sc3+
- Empty d sub-level
4
Q
Why is zinc not a t-metal?
A
- Only forms 1 ion: Zn2+
- Has full d sub-level
5
Q
When ions are formed which e- are removed first?
A
S then D
6
Q
State the physical properties of t-metals
A
- High density
- High MP + BP
- Ionic radii = same
7
Q
State the chemical properties of t-metals
A
- Form complex ions
- Form coloured ions
- Good catalyst
- Variable oxidation state
8
Q
Why do t-metals show variable oxidation states?
A
- Energy level of 4s + 3d sub-level are v close to one another
- So diff. no. e- gained or lost using similar amounts of energy
9
Q
Cu2+
A
Blue
10
Q
Ni2+
A
Green
11
Q
Co2+
A
Pink
12
Q
Fe2+
A
Pale green
13
Q
Mn2+
A
Pink
14
Q
V2+
A
Violet
15
Q
Fe3+
A
Yellow
16
Q
Cr3+
A
Green/violet
17
Q
V3+
A
Green
18
Q
VO2+
A
Blue
19
Q
VO2+
A
Yellow
20
Q
Cr2O72+
A
Orange
21
Q
MnO4-
A
Purple
22
Q
Define complex
A
Central metal atom/ion surrounded by co-ordinately bonded ligands
23
Q
Define co-ordinate bond
A
Covelant bond where both e- in shared pair come from same atom/ligand
24
Q
Define ligand
A
Atom, ion or molecule that donates pair of e- to central t-metal to form co-ordinate bond
25
Define co-ordinate no.
**No. of co-ordinate bonds formed** w/ **central metal ion**
26
Which ligands do t-metals form octahedral complexes w/?
* **Small ligands**
* Eg. **H2O, NH3**
27
Which ligands do t-metals form tetrahedral complexes w/?
* **Larger ligands**
* eg. **Cl-**
28
What shape does 6 co-ordinate bonds form + what is the bond angle?
* **Octahedral**
* **90º**
29
What shapes do 4 co-ordinate bonds form + what is the bond angle?
* **Tetrahedral**: **109.5º**
* **Square planar**: **90º** (**cisplatin**)
30
What shape does some silver complexes w/ 2 co-ordinate bonds form + what is the bond angle?
* **Linear**
* **180º**
31
What is the overall charge on the complex ion?
**Total oxidation state**
32
Oxidation state of metal ion equation
**Oxidation state of metal ion = total oxidation state - sum of oxidation states of ligands**
33
Give an example of a linear complex + what it's used for
* **[Ag(NH3)2]+**
* **Tollen's reagent**
34
# Define monodentate
Give examples
**Ligand** that can **only form 1 co-ordinate bond**
## Footnote
**H2O, NH3, Cl-**
35
# Define multidentate
Give examples
**Ligand** that can **form more than 1 co-ordinate bond**
## Footnote
**EDTA4-**
36
What does EDTA4- stand for?
**ethane diomine tetra acetate**
37
# Define bidentate
Give examples
**Multidentate ligands** that **form 2 co-ordinate bonds**
- **ethane-1,2-diamine** (**H2NCH2CH2NH2**)
- **ethandioate** (**C2O42-**)
38
What is haem?
**Iron (II) complex** w/ **multidentate ligand**
39
Why is haemoglobin important?
**O2 co-ordinately bonds** to **Fe2+** to form **oxyhaemoglobin** + is carries **O2 round bod**y in **blood**
40
Why is CO dangerous?
* **Co-ordinately bonds** to **Fe2+** instead of **O2**, forming **carboxyhaemoglobin**
* **CO** is a **strong ligan**d + **doesn't readily exchange** w/ **H2O/O2 ligands**
* Unable to transport O2 round body
* Causes: **headaches, dizziness + death**
41
Define optical isomerism
Ions can exist in **2 forms** that are **non-superimposable mirror images**
42
Which complexes show optical isomerism?
**Octahedral complexes** w/ **bidentate ligands**
43
Which complexes form + display cis-trans isomerism?
* **Octahedral complexes (monodentate ligand)**
* **Square planar**
44
What is the cis isomer of cisplatin used for?
**Anti-cancer drugs**
45
When does the 3d orbital split into 2 diff energy levels?
**Ligands bond** to **ions** + causes **orbitals** to **gain energy**
46
Which orbitals do e- tend to occupy?
**Lower orbitals**
47
Where does e- get energy from to jump up to the higher orbitals?
**Visible light**
48
What happens when visible light hits a t-metal ion?
**d e-** move from **ground state** to **excited state**
49
How does colour arise in t-metals?
* Some **wavelengths** of **visible light** are **absorbed**
* **Rest** of **freq**. **transmitted/reflected**
50
What does the freq. absorbed depend on?
**Size** of the **energy gap ΔE**
51
What happens when the frequencies are reflected/transmitted?
**Freq combines** to make **compliment** of **colour** of absorbed freq - **colour you see**
52
What is the colour when there are no 3d e- or 3d sub-level is full?
* **Colourless**
* Bc **no e-** will **jump** so **no energy absorbed**
53
The larger the gap the\_\_\_ the feq. of light that is absorbed
**Higher**
54
How can the colour of a complex be altered?
By **change size** of **energy gap**
* Change in:
* **Oxidation state**
* **Co-ordination no.**
* **Ligand**
55
What can be used to find the conc of t-metal ions?
* **Spectroscopy**
* **White light shone through filter**, chosen to **only let colour of light absorbed** by **sample**
* **Light passes through** sample to **colorimeter** - **calculates** **how much light** is **absorbed**
* **More conc = more light absorbed**
56
What must be produced before finding the unknown conc of a sample?
* **Calibration curve** - measuring **absorbance** of **known conc** of solutions + **plot** on graph
* **Measure absorbance** of **sample** + **read off graph**
57
# Define ligand substitution
What does it usually result in?
* **Ligands changing places** w/ another
* **Colour change**
58
What happens to the co-ordination no. + shape of a complex ion if the ligands are similar size + same charge?
**Nothing**
59
Why is substitution btw H2O + NH3 easy?
* **Similar size**
* **Both uncharged**
60
What happens to the co-ordination no. + shape of a complex ion if the ligands are diff. size?
**Changes**
61
Why is the enthalpy change for a ligand exchange reaction v small?
**Strength** of **bonds** being **broken** is v **similar** to **bonds formed**
62
What is the chelate effect?
When **monodentate** ligands are **substituted** w/ **bidentate** + **multidentate** ligands, **inc** in **stability**, no. **particles inc**, so **greater entropy** - **more likely** to occur
63
What is used to reduce vanadium ions?
**Zinc** metal in **acidic solution**
64
How is the stability of an ion affected the larger the redox potential?
**Less stable**, **more likely** to be **reduced**
65
How is the redox potential affected in an acidic solution?
**Larger redox potential**, easier to reduce
66
Outline how to carry out a titration to find out how much oxidising agent is needed to react w/ a quantity of reducing agent
* Measure out **reducing agent** using **pipette** + put into **CF**
* Using measuring cylinder, add **dliute sulfuric acid** to flask
* Add **oxidising agent** (**aqueous potassium manganate**) to reducing agent using burette
* Add until the mixture changes colour to **purple**
67
How do transition metals work as catalysts?
**Changing oxidation states**
68
Outline heterogeneous catalyst
* **Diff phase** to reactants
* Reaction happens at **active site** on **surface** of **catalyst**
* **Support mediums** used to **max. SA** + **minimise cost**
69
Give examples when heterogenous catalysts are used
* **Iron** in **haber process** to make **ammonia**
* **Vanadium oxide** in **contact process** to make **sulfuric acid**
70
What is the problem in using hetrogenous catalysts?
Give example
* **Impurities** **bind** to **catalyst surface** + **block reactants** from being **adsorbed** - **catalyst poisoning**
* **Reduces SA**, **slowing down reaction**
* **Inc cost**
* **Sulfur poisons iron catalyst** in haber process, H produced from **methane**, sulfur reacts w/ iron to produce **iron sulfide**
71
Outline the process of heterogenous catalyst
* **Diffusion**
* **Adsorption**
* **React (bonds broken/formed)**
* **Desorption**
* **Diffusion**
72
Outline homogneous catalyst
* **Same phase** as reactants
* Work by forming **intermediate species** which **react** to form products + **re-form catalyst**
73
Why is the reaction btw iodide ions + peroxidisulfate slow?
How can you over come this problem?
* **Both ions -ve charged** so **repel**, **less likely** to **collide**
* **Add Fe2+** ions bc +ve ion so **no repulsion**
74
Define autocatalyst
**Product** of reaction **catalyses reaction**
