CHAPTER 24 - TRANSITION ELEMENTS Flashcards
Where are d block elements found on the periodic table
Between Group 2 and Group 13 (Scandium to Zinc)
What are the properties of d-block elements
High MP+BP
Shiny appearance
Conduct Electricity and Heat
What are some uses for d-block elements
Construction and tools (Fe)
cables and water pipes (Cu)
Aerospace and Joint replacement (Ti)
Coins (Cu, Ni, Zn)
What are the exceptions to electron configurations in d-block elements
Chromium and Copper
Why do Chromium and Copper not fulfil the normal electron configurations
Half filled d5 and fully filled d10 sub-shells are more stable
What are the general rules for formation of atoms and ions in d-block elements
When forming an atom, 4s orbital FILLS before the 3d orbitals
When forming an ion, 4s EMPTIES before 3d orbitals
What are transition elements
d-block elements that form at least one ion with a partially filled d-orbital
Which d-block elements are not classified as transition elements and why
Scandium and Zinc
Dont form at least one ion with a partially filled d-orbital
Properties of transition metals and their compounds
High MP+BP
Conduct Electricity and Heat
Variable oxidation states
Coloured compounds
Catalysts
Variable oxidation states and colours
Pg 402 - Table
What colours do the two most common oxidation states of iron and chromium each form when dissolved in water
Iron (II) - Pale green
Iron (III) - Yellow
Chromium (III) - Green
Chromium (VI) - Yellow/orange
How do Transition metals act as catalysts
Increases rate of reaction
Provides Alternative pathway
Lowers Ea
Remains chemically unchanged
Examples of transition metals as catalysts?
Haber Process - Iron
Contact Process - V2O5
Hydrogenation of Vegetable oils - Nickel
Decomposition of H2O2 - MnO2
What are Complex ions?
When one or more molecule or negatively charged ion(s) (ligands) bond to a central metal ion
What is a Ligand
A molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond or a dative covalent bond
What is a Dative covalent/coordinate bond?
A covalent bond where one atom provides both of the electrons for the shared pair
What is a coordination number
Shows how many bond are attached to a central metal ion
How are complex ions represented
Complex ion inside square brackets with charge on outside
eg. [Cr(H2O)6] 3+
Name an uncharged ligand
Water
What are monodentate ligands
Ligand able to donate one pair of electrons to a central ion
eg. H2O, NH3, Cl-, CN-, OH-
What is a Bidentate ligand?
Ligand which can donate two lone pairs to the central metal ion, forming two coordinate bonds
eg. 1,2 diaminoethane and ethanedioate (pg 406)
What shape do six-coordinate complexes form?
Octahedral
90 degree bond angle
2 bonds straight
2 bond into
2 bonds out of
(pg 407)
What shapes do four-coordinate complexes form?
Tetrahedral
109.5 angle
2 straight
1 in and 1 out of
Square Planar
90 angle
2 in 2 out
What are the stereoisomers in complex ions
Optical isomerism
Cis-trans isomerism
What happens when ammonia is added to a solution of [Cu(H2O)6] 2+
Light blue to dark blue ppt
What happens when Chloride ions are added to a solution of [Cu(H2O)6] 2+
Pale blue to yellow colour change - shape change from octahedral to tetrahedral
What happens when aqueous ammonia is added to [Cr(H2O)6] 3+
grey-green to purple
What happens when haemoglobin binds to oxygen
Fe2+ binds to oxygen gas, in the capillaries of the lungs
Forms Oxyhaemoglobin, which releases this oxygen to body cells when required
What happens when carbon dioxide binds to haemoglobin
CO2 binds to Haemoglobin in RBCs
Released from the red blood cells and exhaled
What happens when Carbon Monoxide binds to Haemoglobin
Binds to Fe2+, forming Carboxyhaemoglobin
If carbon monoxide is breathed in, a ligand substitution reaction takes place where the oxygen is replaced by Carbon monoxide, bonding more strongly
So a small amount of CO can cause large proportion of haemoglobin molecules carrying oxygen
Forms irreversible reaction, when concentration of carboxyhaemoglobin is too high, oxygen transport is prevented, leading to death.
What makes a precipitate
When two aqueous solutions containing ions react together to form an insoluble ionic solid (ppt)
(usually Dissolvable in excess NaOH)
What colours do Fe2+, Fe3+, Cu2+ and Mn2+ form when reacting with Aqueous NaOH
Fe(OH)2: Green, Orange-brown in air
Fe(OH)3: Orange-brown
Cu(OH)2: Blue (dissolves in excess NH3)
Mn(OH)2: Light-brown
What colour ppt is formed when Chromium 3+ reacts with NaOH ions?
Green / Dark Green ppt
(dissolves with excess ammonia - forms new complex ion)
How is Iron oxidised from Fe2+ to Fe3+?
MnO4- is reduced to Mn2-
Purple solution of MnO4- when iron is added turns colourless
What happens when iron is reduced from Fe3+ to Fe2+
I- ions react with the Orange-brown Fe3+ ions are reduced to pale-green Fe2+ ions
I- is oxidised to I2
What is the colour change from Cr2O7 2- to Cr3+ ions, the a further reduction to Cr2+ ions using excess Zinc
Orange to green
Then green to Pale Blue
What oxidation state is chromium oxidised from Cr3+ to CrO4 2-
Cr3+ to Cr6+
3H2O2 + 2Cr3+ + 10OH- = 2CrO4 2- + 8H2O
What is the equation when copper is oxidised and what colour change is seen
2Cu2+ + 4I- = 2CuI + I2
Pale blue - White Ppt + Brown solution
How can you tell if ammonium ions have reacted with OH- ions?
Forms NH3 + H2O
Damp red indicator will turn blue if NH4+ ions are present
What is the chemical test for carbonate ion and what is observed?
Add dilute HNO3, effervescence seen
What is the chemical test for sulfate ion and what is observed?
Add Ba2+ ions , forms white ppt (BaSO4)
What is the chemical test for Halide ions and what is observed?
Add Ag+ ions
Will form AgX
AgCl - white ppt in dilute NH3
AgBr - cream ppt in conc NH3
AgI - Yellow ppt - insoluble
