5.3.1 Transition Elemtns and 5.3.2 Qualitative Analysis Flashcards
Define a transition element
A d block element that forms atleast one stable ion with partially filled d subshell
Where are the transition metals located in the periodic table?
In the middle block from Ti to Cu
What are the 2 elements in the d block that are not considered as transition metals?
Scandium and Zinc
Why is scandium and zinc not considered as transition metals?
Scandium only forms Sc3+, where the d orbitals are empty
Zinc only forms Zn2+ where the d orbitals are full
What is the noble gas configuration of chromium
[Ar] 4s1 3d5
What is the noble gas configuration of copper?
[Ar] 4s1 3d10
Which electrons do transition metals lose first when forming ions?
4s
What are some characteristic physical properties of transition metals?
Metallic high density high mp and bp shiny good conductor of heat and electricity
What are the characteristic chemical properties of transition metals?
Variable oxidation states
take part in any redox reactions
Coloured compounds / ions in solution
Good catalysts
Form complex ions
In potassium manganate (Vll), what is the oxidation number of Mn?
Mn =+7
What are the 2 main ways in which transition metals act as an effective catalyst?
They provide a surface on which reaction can take place
They change oxidation states to form intermediates required for pathways with lower activation energy
Give some examples of transition metal catalysts and the processes / reactions they catalyse (4)?
iron - haber process
Vanadium (V) oxide - contact process
Nickel - hydrogenation of alkenes
Manganese (IV) oxide - decomposition of hydrogen peroxide
copper sulfate - hydrogen production
What is a complex ion?
Transition metal ion bonded to one or more ligands by coordinate bonds
Define a ligand
Molecule or an ion that can donate a pair of electrons o the metal to form a coordinate bond
What is a coordinate bond?
A bond in which one of the atom provides both the electrons required for bonding, also known as dative bonding
What does the coordination number indicate
The number of coordinate bonds formed between the metal ion and its ligands
What is a mono/unidentate ligand
a ligand that forms one coordinate bond to the central metal ion ( one lone pair to donate)
What is a bidentate ligand?
A ligand that forms two coordinate bonds to the central metal ion (2 lone pairs to donate)
What is a multidentate ligand?
A ligand that forms three or more coordinate bonds to the central metal ion
Give some examples of common monodentate ligands
Cl-
H2O
NH3
CN-
Name the most common bidentate ligand
ethane-1,2-diamine
How many coordinate bonds does EDTA 4- form?
6
EDTA is a chelating agent, what does that mean?
EDTA decreases the concentration of metal ions in the solution by binding to them and forming complex ions
What ion is usually formed when a transition metal compound is dissolved in water?
What shape is it?
Aqua ion, 6 H2O ligands around the central metal ion. Octahedral complex ion is formed
If a transition metal ion has 2 ligands, what shape is it usually?
linear
If a transition metal ion has 4 ligands, what shape is it usually
Tetrahedral
Name as exception to the general rule that ions with 4 ligands is generally tetrahedral. What shape is it?
Platin is square planar
forms cisplatin
What shape is a complex ion if it has 6 ligands?
Octahedral
How can complex ions display EZ pr zis trans isomerism? What shapes of ions does this apply to?
Ligands differ in the way in which they are arranged in space.
2 ligands of the same type can be on the same side of the metal ion (next to each other), which forms the E or cis isomer.
2 ligands of the same type can be opposite sides of the metal ion (not next to each other), which forms the Z or trans isomer.
Applies to square planar and octahedral complex ions
What conditions are needed for a complex ion to display optical isomerism?
Usually applies to octahedral molecules with 2 or more bidentate ligands, so that the mirror images are non-superimposable
What is cis-platin used for?
Describe its mechanism of action
I is used as an anti-cancer drug
It binds to DNA of fast growing cancer cells and prevents cell division, hence reducing the growth of cancer
Which metal ion is present in a haem group?
FE2+
What is the coordination number of a haem group?
6
What are the ligands in haem group?
4 nitrogen forming the porphyrin ring
1 oxygen
1 globin
Why is CO toxic?
CO also coordinately bonds to the Fe 2+, and bonds more strongly to FE 2+ than O2.
Stops O2 from bonding to haemoglobin, so O2 cannot be transported around the body
What colour is [Cu(H2O)2+ solution?
Pale blue
What colour is [Cu(NH3)4(H2O)2] 2+ solution?
Deep blue
What colour is [ CuCl4]2- solution?
Yellow
What colour is [Cr(H2O)6] 3+ solution?
Dark green
What is a precipitation reaction?
A reaction where soluble ions in separate solutions are mixed to form an insoluble compound
What colour is Fe 2+ aqua ion?
Green
What colour is Fe3+ aqua ion?
Pale brown
What colour is Cr3+ aqua ion?
Violet
What colour is Mn2+ aqua ion?
Pink
When Cu2+ reacts with NH3 or OH-, what colour is the precipitate?
Blue
When Fe2+ reacts with NH3 or OH-, what colour is the precipitate?
Green
When Mn2+ reacts with NH3 or OH-, what colour is the precipitate?
Brown
When Cr3+ reacts with NH3 or OH-, what colour is the precipitate?
Green
When Fe 3+ reacts with NH3 or OH-, what colour is the precipitate?
Brown
What colour is MnO4-
purple
Write a half equation for the reduction of MnO4 - to Mn 2+
MnO4 - + 8 H+ + 5e- –> Mn 2+ + 4 H2O
Why are redox titrations with transition metal compounds said to b awlf indicating?
They usually involve a colour change as the metal is changing oxidation state; sometimes an indicator is still needed / useful
What colour is Cr2O7 2-?
Orange
What colour is Cr3+?
Green
Write a half equation for the reduction of Cr2O7 2- to Cr3+
Cr2O7 2- + 14 H+ + 6e- —> 2 Cr 3+ + 7H2O
Describe how to test for metal ions
Fill half of the test tube with the sample
Add aqueous ammonia or sodium hydroxide drop by drop
Colour of precipitate indicates the ion present
Write the method used to test fpr ammonium ions
Fill half the test tube with sample
Add sodium hydroxide and warm gently
Smelly gas is produced; damp red litmus paper turns blue
Why does lime water turn milky in the presence of carbon dioxide?
When carbon dioxide is bubbled in calcium hydroxide (lime water), calcium carbonate precipitate is formed.
