Transitional Elements Flashcards
Where is the highest energy electron in the first row of d block elements?
in their 3d sub-shells
why does the 4s subshell fill before the 3d subshell?
Because the 4S subshell is at a lower energy than the 3d subshell
what is a D block element?
One which has its highest energy electrons in a D sub shell
What is the definition of a transition metal?
A transition metal is a d-block element that has an ion with an incomplete d subshell
What happens when a transition element forms a positive ion?
it loses it’s valence (outer shell) electrons first.
This means that the 4s electrons are removed before any d-electrons
how would I explain why a metal is a transitional element?
e- configuration
incomplete d subshell
so therefore transition element
Why is zinc not a transition element?
Zn2+ has a complete d-subshell so does not form and least one ion with an incomplete d-subshell. Therefore Zn is not a transition element
what are the properties of transition elements?
-Variable oxidation states
-Formation of coloured compounds and ions
-Catalytic Behaviour
What are transition elements able to form?
more than one stable oxidation state (seen in their ions)
why are transition elements able to form more than one stable oxidation state?
because the electrons in the 3-D subshells are close together in energy, so it’s almost as easy to remove several electrons as it is to remove just one
What are common oxidation states for iron?
+2
+3
what are common oxidation states for copper?
+1
+2
what are the solutions of transition elements and their oxyanions?
they are coloured e.g. cu2+ (aq)
what happens when copper sulphate dissolves in solution? (coloured compounds)?
Cu2+(aq) ions are released and the solution appears blue
What can Cu2+ (aq) be represented as?
a complex ion [Cu(H2O)6]2+
what are transition elements and their compounds very good at being?
catalysts (both homogenous and heterogenous)
what is two reasons why transition elements are very good catalysts?
-they can have different oxidation state so ions can gain or lose electrons easily
-The empty de orbitals can accept electrons from other molecules/ions at the transition element surface. Intermediate species can be made.
What reaction is iron (s) a catalyst in?
haber process- N2 (g) + 3H2(g)—> 2NH3(g)
What reaction is V2O5 (s) a catalyst in?
contact process- 2SO2(g) + O2(g)—>2SO3(g)
This process occurs via the following mechanistic steps
What mechanistic steps do the contact process occurs via?
1- SO2(g) + V2O5(s)—> SO3(g) + V2O4(s)
2- V2O4(s) + ½O2(g)—> V2O5(s)
Here the V2O5 is believed to react with SO2 to form V2O4 and SO3 and then the V2O4 reacts with the oxygen to regenerate the V2O5. V changes from a +5 oxidation state
to a +4 one and back again.
What reaction is nickel a catalyst in?
Hydrogenation of alkenes (unsaturated oils can be hydrogenated to make margarine)
0.16 mol of an alkene containing 8C reacts with 15.36 dm3 of hydrogen in the presence of a nickel catalyst. How many carbon-carbon double bonds does the alkene molecule contain?
aH2:H2
0.16:0.64
1 : 4
= 4 double bonds
when do transition metals form complex ions?
when a salt or compound of the metal is dissolved in water. The metal ion does not exist in isolation, it develops bonding interactions with the molecules which are present in solution. So, for example, when copper(II)chloride (CuCl2) is dissolved in water the Cu2+ and the Cl- ions become separated from each other and will make bonding interactions with the surrounding water molecules.
what is the definition of a complex?
A complex consists of a central metal ion bonded by molecules or negatively charged ions. These molecules or ions are called ligand
what is the definition of a ligand?
A ligand is a molecule or an ion, which donates a lone pair of electrons to the central metal ion by co-ordinate bonding (dative covalent bonding).
what are common ligands?
include: H2O, Cl-, NH3, OH-, CN- and SCN-
(some charged some neutral; all have a lone pair of electrons)
which is an example of a complex ion with a neutral ligand?
[Cu(H2O)]6 2+
Why is the charge of the complex ion the same as the central metal ion?
Water is a neutral ligand
what is incorporated when writing formulae of complex ions involving negatively charged ligands?
the charge of the ligand is incorporated into the overall charge of the complex ion.
what is the definition of the coordination number?
The co-ordination number is the number of co-ordinate bonds in the
complex (not necessarily the number of ligands)
Why can a hydroxide ion behave as a ligand?
The O has a pair of electrons which form a coordinate bond with the central metal ion through donation of that lone pair
how many bonding pairs and lone pairs does water have when it’s gas?
2 bonding 2 lone
how many bonding pairs and lone pairs has does water have when it is a ligand?
3 bonding 1 lone
How many bonding pairs and loan pairs does ammonia have when it is a gas?
3 bonding, 1 lone
how many bonding pairs and loan pairs does ammonia as a ligand have?
4 bonding, 0 lone
what is the formulae of the two ions which will be present when anhydrous K4[Fe(CN)6)
K+
[Fe(CN)6)]4-
Sodium cyanide (NaCN) is a source of cyanide ions. Explain why solid sodium cyanide does not conduct electricity, whereas a solution would.
as a solid NaCN does not conduct electricity, ions are fixed in the lattice so cannot move
In solution, the ions are mobile so can conduct
what is the definition of a bidendate ligand?
ligand that can donate two pairs of electrons to the central metal ion,
to make two coordinate bonds,
What is a Poly/multidentate?
a ligand which donates more than two pairs
What will three bidendate ligands make?
a six-coordinate complex
What are the atoms/species
which donate the electrons in a ligand?
usually: N, O, O-, P, Br-.
what must you look for in order to spot atoms which are able to act as ligands?
nitrogen atoms with 3 bonds, oxygen atoms with a negative charge
What do ions of carboxylic acids (carboxylate ions) coordinate through?
the lone pair of the O- only.
What is a common example of a bidendate ligand?
the ethanedioate ion (C2O42-).
What is another common bidendate ligand?
is 1,2 diaminoethane. This is a neutral ligand.
You sometimes see it represented as “en”. It is better to represent it in displayed,
The molecule below is called 18-crown-6-ether. What allows it to behave as a polydentate ligand?
The pair of electrons on each O
what are the three shapes of complex ions?
Tetrahedral
Octahedral
Square planar
what are the bond angles for octahedral?
90 degrees
what is the bond angle for tetrahedral?
109.5
What is cisplatin?
[PtCl2(NH3)2]
an example of square planar
What is the bond angle and co ordination number for square planar?
90 degrees
4
what is cisplatin?
A very effective anti-cancer drug that binds to DNA preventing cell division
What can many complexes exist as?
stereoisomers; they have the same structural formulae but different spatial arrangements of their atoms
what are the two types of stereoisomers?
cis/trans
isomers and optical isomers.
Where do cis/trans isomers only happen?
square planar or octahedral complexes- there needs to be two of the same monodendate ligands present
what are the differences in the bond angles Cl-Pt-Cl (cis platin) in cis and trans?
cis-90 degrees
trans- 180 degrees
Why would using alanine rather than glycine as a ligand increase the number of stereoisomers possible?
The carbon bonded to the CH and the NH2 is chiral which means that six isomers are possible
What show optical isomerism?
Octahedral complexes which have two or more bidentate ligands
As a result of their (octahedral complexes) 3D shape, what is possible?
there are two possible mirror image isomers, which are non-super imposable. The central ion is not described as chiral; this term is reserved for organic molecules only.
What do transition ions react with to give a precipitate?
hydroxide ion in aqueous solution
What is a precipitate?
a solid on the inside of the test tube
what colour is Cu(OH)2 (s)
pale green
What color is Fe(OH)2 (s)?
the green solid
What color is Fe(OH)2 (s)?
similar to rust, orange-brown ppt
What color is Mn(OH)2 (s)?
light brown solid
what colour is Cr(OH)3 (s)?
grey-green ppt
What is the general equation for the precipitate reactions with sodium hydroxide?
Mx + xOH- —> M(OH)x (s)
what are the precipitate reactions?
Mn2+(aq) + 2OH-(aq) → Mn(OH)2(s) (light brown)
Cu2+(aq) + 2OH-(aq) → Cu(OH)2(s) (pale blue)
Fe2+(aq) + 2OH-(aq) → Fe(OH)2(s)
(green)
Fe3+(aq) + 3OH-(aq) → Fe(OH)3(s) (orange/brown) (rust)
Cr3+(aq) + 3OH-(aq) → Cr(OH)3(s) (grey green)
What are Cu(OH)2 , Fe(OH)2 , Fe(OH)3 and Mn(OH)2 in excess sodium hydroxide and what does his mean
insoluble in excess sodium
hydroxide so the solid remains present in these reactions.
What can Cr(OH)3 do?
can react further with sodium hydroxide so redissolves and forms a dark-green solution.
(Cr(OH)3(s) + 3OH-(aq) → [Cr(OH)6]3-(aq)
Grey-Green ppt Dark Green Solution)
what is the overall equation for the reaction of cr(OH)3 (s) with excess sodium hydroxide?
[Cr(H2O)6]3+ + 6OH- —> ]Cr(OH)6]3- + 6H2O
what do small amounts of ammonia in water act as and what does this mean? and equation)
-as a source of hydroxide ions.
NH3 + H2O → NH4+ + OH-
-means that when small amounts of ammonia are added to aqueous solutions of Mn2+,Cu2+,Fe2+,Fe3+ and Cr3+, the same reactions occur as those in the table
What behaves differently with ammonia?
Cu2+ and Cr3+
What is ligand substitution?
-Electron pair donors in one complex can be replaced by other ligands to form more stable complexes.
-Often the reactions are reversible
What are the ligand substitution reactions?
-Copper (II) ions and excess ammonia
-Chromium (III) ions and excess ammonia
-c) Copper(II) ions and concentrated HCl (aq)
What happens in the reaction of Copper (II) ions and excess ammonia?
Upon dropwise addition of ammonia to the Cu2+(aq) : a pale blue precipitate is observed. This precipitate dissolves in excess ammonia to give a deep blue
solution. There are two reactions. The first is where ammonia acts a base with water to produce ammonium hydroxide, resulting in a precipitation reaction. The second is where the ammonia takes part in ligand substitution.
What are the equations for the reaction of copper (II) ions with excess ammonia?
- Cu2+(aq) + 2OH-(aq) → Cu(OH)2(s)
blue solution pale blue precipitate
This is precipitation, not ligand substitution. - [Cu(H2O)6]2+(aq)+ 4NH3(aq) [Cu(NH3)4(H2O)2]2+(aq) + 4H2O(l)
blue solution dark blue solution
This is ligand substitution.
What are the equations for the reaction between Chromium (III) ions and excess ammonia?
- Cr3+(aq) + 3OH-(aq) → Cr(OH)3(s)
Violet / green solution This is precipitation, not ligand substitution
grey-green precipitate
Note Cr3+(aq) is a violet solution, not green. - [Cr(H2O)6]3+(aq) + 6NH3(aq) violet / green solution [Cr(NH3)6]3+(aq) + 6H2O(l) purple solution
What happens in the reaction between Copper(II) ions and concentrated HCl (aq)?
On addition of the HCl(aq) the blue solution turns yellow. H+ is spectator ion so does not appear in the equation. The solution might appear green if both ions are present.
What are the equations for the reaction between Copper(II) ions and concentrated HCl (aq)?
Cu(H2O)6]2+ (aq) + 4Cl-(aq) octahedral (blue solution) [CuCl4 ]2- (aq) + 6H2O(l)
tetrahedral (yellow solution)
The above reaction is reversible; it is an example of equilibrium.
Explain the observation when an excess of concentrated hydrochloric acid is added to aqueous copper sulfate.
colour change from blue to more yellow as equilibrium shifts to the right
what is a ligand substitution important in?
in the transport of oxygen by haemoglobin (Hb).
Why is ligand substitution is important in the transport of oxygen by haemoglobin (Hb)?
-The active part, Haem contains an -Fe (II) ion which forms four co-ordinate bonds to the four nitrogen atoms in the haem ligand and to one nitrogen atom in the globin. Oxygen gas (O2) can also form a bond with the Fe2+, this allows it to be transported around the body.
with reference to haemoglobin explain why carbon monoxide is toxic
-CO can also act as a ligand with iron (II) ions and replace O2 in a ligand substitution reaction.
-The CO forms a stronger bond with the Fe2+ in the haemoglobin than O2.
- this makes it toxic by inhalation
what is the element that has atoms with an average of 8.64×10 to the power of -23 g?
chromium
What can cr3+ ions be reduce further by?
the addition of Zn solid
Zn(s) + 2Cr3+(aq) → Zn2+(aq) + 2Cr2+(aq)
Green solution(sulfate ion still present) Pale blue
When cr3+ ions are in the presence of sulfuric acid (required for oxidation of alcohols) what can sulfate ions act as?
as a ligand to form [Cr(H2O)5(SO4)]+ (aq). This is a green solution
What do chromium(III) ions in water (Cr3+(aq) or [Cr(H2O)6]3+) with no sulfate ions present?
a violet solution.
what is the equation for the reduction of CU2+ plus Cu+?
2Cu2+(aq) + 4I-(aq) → 2CuI(s) + I2(aq)
pale blue solution white ppt. brown solution
What is the equation for the disproportionation of Cu+ to Cu2+ and Cu?
Cu2O(s) + H2SO4(aq) → Cu(s) + CuSO4(aq) + H2O(l)
Brown Solid Blue Solution
