15 transition metals Flashcards
What block are transition metals apart of on periodic table?
D block
How is the electronic config for chromium different?
It has 5 electrons in 3d ( one in each d sub orbital) and 1 in 4s instead of 2 in 4s and 4 in 3d
Why does chromium have its specific electronic config?
It is more stable as the distribution of charge is much more equal
How is the electronic config of copper special?
It has a 3d10, 4s1 config instead of 3d9, 4s2
Why does copper have its specific electronic config?
As it is more stable the having 2 electrons in 4s
How are scandium and zinc different from the rest of the transition metals?
They both have only 1 oxidation state ( scandium +3, zinc +2) whereas transition metal elements have two or more.
Scandium and zinc compounds are usually and white and not coloured.
Scandium, zinc and their compounds show little catalytic activity.
Define transition metal
An element that has one or more stable ions with incompletely filled d orbitals.
What are common characteristics of transition metals?
-Are hard metals with useful mechanical properties, high melting and boiling point
-They show variable oxidation numbers in their compounds
-They form coloured ions in solution
-They can act as catalysts as elements and their compounds
-They form complex ions involving monodentate, bidentate and polydentate ligands
Are transition metals more or less reactive than s block elements?
Much less
What is the least reactive transition metals more or in period 4?
Copper
Why is copper used in domestic water pipes and electricity cables?
It is a good conductor of electricity
Why can most transition metals in period 4 be present in different oxidation states?
Metals from titanium to copper have electrons of similar energy in both 3d and 4s levels. This means that each of these elements can form ions of roughly the same stability in aqueous solution or crystalline solids by losing different numbers of electrons.
As you move along period 4 why does the main oxidation switch from +3 to +2?
This is because as you go along the period, the +2 oxidation state becomes more stable relative to +3.
What is the most effective demonstration of the range of oxidations states in a transition metal?
Shake ammonium vandate(v), NH4VO3, in dilute sulfuric acid with zinc.
Before zinc is added the solution turns yellow to the presence of VO2~+ ions.
When shaken with zinc the solution turns from yellow to blue as its being reduced and forms VO~2+ ions.
Shake more and the solution turns green to the presence of V~3+ ions.
Shake more and the solution is reduced again and turns violet to the presence of v~2+ ions.
What oxidation states can chromium form compounds in?
+2, +3, +6
Which oxidation state of chromium can be oxidised and reduced?
+3 in Cr~3+
What colour are Cr2O7~2- ion?
Orange
What colour are Cr~3+ ions
Green
What is a complex ion?
An ion in which a number of molecules or anions are bound to central metal cation by coordinate bonds.
What is a ligand?
A molecule or anion bound to the central metal ion in a complex ion by coordinate bonding.
What must a ligand have?
At least one lone pair of electrons which it uses to form a dative covalent bond with the metal ion.
What is a co ordinate bond?
Another name for dative covalent bond
What is coordination number of a metal ion?
The number or coordinate bonds to the metal ion from surrounding ligands
What are two common visible signs that a reaction has occurred during the formation of a new complex ion?
- colour change
- insoluble solid dissolving
What is a familiar example of colour change?
Excess ammonia with copper(ii) sulfate solution
What are the steps to naming a complex ion?
1) identify the number of ligands around the central cation using greek prefixes: mono, di, tri …
2) name the ligands using names ending in -o for anions e.g chloro and hydroxo. Aqua for water. Ammine for NH3.
3) name the central metal ion using the normal name of the metal for positive and neutral complex ions and -ate for negative complex ions
4) add oxidation number of central metal ion.
Shape for 6 coordinate bonds?
Generally octahedral
Shape name for four coordinate bonds?
Usually tetrahedral but some are square planar
Shape name with two coordination bonds?
Linear
What are monodentate ligands?
Form one dative covalent/coordinate bond with with central metal ion complex
What are bidentate ligands?
Form two dative covalent/coordinate bonds with a central metal ion complex
What are multidentate ligands?
They form more than one coordinate bonds with a with the same metal ion from
What are chelates?
Complex ions involving multidentate ligands
What is a transition metal?
An element that has one or more stable ions with incompletely filled d orbitals
What colour is VO2 ~ + ?
Yellow
What colour is VO~2+?
Blue
What colour is V~3+?
Green
What colour is V~2+?
Purple
What colour is CuCl4?
Yellow
Why do transition metals in period 4 form a range of compounds in different oxidation states?
As transition metals from titanium to copper have electrons of similar energy in both 3d and 4s levels.
Why do scandium and zinc have white flames?
As they form ions with incomplete or full 3d subshells
Why do H20, OH- and NH3 form monodentate ligands?
As they have one pair of lone electrons each
Why do complexes with six fold coordination have an octahedral shape?
So the 6 lone pairs of electrons around the central atom are repelled as far as possible.
What shape will Cl- form in a complex ion and why?
Will form a tetrahedral shape as the chloride ion is large.
Why can cis platin diffuse through the cell membrane?
As it is neutral
Does tetrahedral or square planar allow cis trans isomerism?
Only square planar allows cis trans isomerism to rise
Why can’t cis platin also contain its trans isomer in a chemotherapy drug?
This is because the trans isomer is not effective as a cancer drug n is more toxic than cis.
What is a common bidentate ligand?
NH2CH2CH2
What is a common multidentate ligand?
EDTA~4-
What complex is haemoglobin?
An iron(ii) complex containing miltidentate ligand
What colour does Cr ~3+ have and what’s its oxidation state?
It has a green colour and a +3 oxidation state
What oxidation state is Cr in Cr2O7~2- and what colour does the compound have?
It has a +6 oxidation and has orange colour
What is oxidation state of Cr in CrO4~2- and what colour does the compound have?
+6 oxidation, yellow colour
What’s the oxidation state of Cr~2+ and what colour does it have?
+2, blue
What colour does cr~3+ with 6 water ligands turn when reacted with small amount of NaOH and in excess? What is the colour of the metal aqua ion originally?
Small amount: green precipitate
Excess: green solution
Original: violet solution
What colour does Fe~2+ turn when reacted with a small amount of NaOH and in excess? What is the original colour of the metal aqua ion?
Small: green precip
Excess: no change
Original: green sol
What colour does Fe~3+ turn when reacted with a small amount of NaOH and in excess? What is the original colour of the metal aqua ion?
Small: brown precip
Excess: no change
Original: yellow sol
What colour does Co~2+ turn when reacted with a small amount of NaOH and in excess? What is the original colour of the metal aqua ion?
Small: blue precip
Excess: no change
Original: pink sol
What colour does Cu~2+ turn when reacted with a small amount of NaOH and in excess? What is the original colour of the metal aqua ion?
Small: blue precip
Excess: no change
Original: blue
What colour does Cr~3+ turn when reacted with a small amount of NH3 and in excess? What is the original colour of the metal aqua ion?
All same as NaOH except:
Excess: purple sol
What colour does Co~2+ turn when reacted with a small amount of NH3 and in excess? What is the original colour of the metal aqua ion??
Same as NaOH but
Excess: yellow sol
What colour does Cu~2+ turn when reacted with a small amount of NH3 and in excess? What is the original colour of the metal aqua ion?
Same as NH3 but
Excess: dark blue sol
Why is the reaction of Cu~2+ and ammonia special?
As partial substitution occurs and only 4 water ligands are displaced, not all 6
What does amphiteric mean?
Can act as a base or acid
What are the steps with a heterogeneous catalyst?
Adsorption
Reaction
Desoprtion
What is adsorption?
Process when atoms, molecules or ions are held onto the surface of a solid
What is desorption?
When atoms molecules or ions are released from a solid surface
Where do heterogeneous catalysts adsorb reactants?
On the catalysts active site on surface
Why must the adsorption of the catalyst not be too strong or too weak?
Too strong: molecules remain on surface which prevents further reaction
Too weak: little adsorption occurs and so rate of reaction is very slow
Why are transition metals good catalysts?
As they have variable oxidation states so can easily gain and lose electrons
What is an example of a catalyst that is too strong?
Tungsten
What is used to make H2SO4 in the contact process?
Vanadium(v) oxide
What does V2O5 do in making sulfuric acid?
Turns SO2 to SO3
What happens to the vanadium oxide as it oxidises SO2 to SO3?
It’s is reduced from vanadium(v) oxide to vanadium(iv) oxide
What happens to V2O4 in contact process?
It is reoxidised back to V2O5 by the oxygen in mixture of reacting gases
What is a poisoned catalyst?
When impurities are bound onto the catalyst and block the active sites for reactants to adsorb
What does a poisoned catalyst mean?
Less product made
Catalyst needs to be replaced or cleaned more often
Increased cost of chemical process
What is a homogenous catalyst?
One that forms an intermediate species by reactants combining with catalyst which react to form products. The catalyst is reformed again.
What is autocatalysis?
It’s another form of homogeneous catalysis where the product catalysis the reaction. The amount of product increases and so does rate of reaction
