Transition Metals Flashcards
A transition element is a ____________ _______ which forms ______________ s_____ s_____ ion in which there is a ________-_______ _ subshell.
A transition element is a d-block element which forms at least one stable simple ion in which there is a partially filled d subshell.
Why atomic radii of transition elements smaller than typical S block element, Ca?
Increase in nuclear charge
Shielding effect by inner shells of electrons remain relatively constant as 3d electrons provide relatively poor screening effect.
Effective nuclear charge higher for transition elements than Ca.
Stronger electrostatic attraction between the valence electrons and nucleus -> smaller atomic radius for transition elements.
Why ionic radii of transition elements smaller than corresponding atomic radii?
4s electrons were removed to form the ions
Ions have one less PQ shell compared to atoms.
Name and describe one important chemical property of transition elements?
Variable oxidation states.
Can form compounds in a range of oxidation states due to
CLOSE similarity in energy of 3d and 4s electrons.
What is a ligand?
An ___ or ________ which contains at least one atom bearing one ____ of e________ which can be donated into the energetically _____________ vacant orbital of the central _____atom or ion forming a ______________ (dative) bond.
Ion or molecule (Cl-, OH-,H2O, NH3 etc)
Bearing ONE PAIR OF ELECTRONS
which can be DONATED into energetically ACCESSIBLE vacant orbital of central METAL ATOM OR ION
Forming a co-ordinate (dative) bond
Occurrence of colour in transition metal complexes -> explain how?
Complex ion initially has one set of 3d orbital, degenerate, a happy family. THEN:
📌presence of ligands (slut)
📌3d orbitals split into 2 sets of orbitals with different energies.
📌Difference in energies between 2 sets of 3d orbitals relatively small
📌When an electron moves from orbital of lower energy to partially filled/empty d orbitals of higher energy
📌absorb radiation from the visible electromagnetic spectrum
📌colour observed is complementary of colour absorbed.
What must metals possess to display colour?
- At least one d electron
2. An empty or partially filled upper level to accommodate d electron to be promoted
Steps to check if something is a transition element?
- List electronic configuration.
- See if they have partially filled d orbitals!
- **some oxidation states of some transition metals ARE NOT TRANSITION ELEMENTS.
- Sc and Zn do not have ions with partially-filled 3d subshells-> not transition elements.
- Cu+ NOT, Cu2+ is! (hence former colourless, latter has colour)
Factors affecting colour of complexes
Dependent on energy gap between two sets of d orbitals, in turn dependent on
1) _______ of central metal atom or ion
2) _______ of ligand
- NATURE of central metal atom or ion -> different metals different energy gaps + oxidation state -> compounds of same element in different oxidation states show different colours
- NATURE of ligand
Energy gap between two groups of d orbitals depend on type of ligand -> different ligands split d orbitals by different amount (extent).
Ligand exchange reactions are??
Very duh, just look at equation, one displaces the other. (Oxidation state does change!!)
What is Ks? Give the equation and meaning.
Ks is like Kp/Kc, concentration of products over reactants. Same thing, coefficient is power.
It is the inherent tendency of a particular ligand to replace water in the aqua-complex.
Higher Ks -> stronger binding ligand.
Are ligand exchange reactions reversible? What is the consequence?
Yes!
Relative concentrations of ligand will influence the ligand exchange. (LCP)
Effect of ligand exchange on E(nought) values? Think of Fe example.
Other ligands replace water ligands (H2O) in an aqua complex -> can cause LARGE CHANGES in electrode potential values.
Replacing H2O with stronger binding CN- causes E(naught) for the Fe3+/Fe2+ system to become less positive -> means more favourable for oxidation, less for reduction -> Fe3+ a weaker oxidising agent.
What is haemoglobin?
Red pigment in blood, carries oxygen from lungs to cells of body.
What are the bitchy, evil, ligands?? Aka poisonous.
Explain in relation to haemoglobin.
CN- and CO
Can replace water molecule of haemoglobin, strongly and often IRREVERSIBLY adsorbed at this site, destroys haemoglobin’s oxygen-carrying capacity.
Reactions of transition metal complexes
Chromium (Cr)
Is it acidic or basic? Reacts with carbonates to give? Reacts with metals to give?
When NaOH added to Cr3+ solution what is formed? In excess how?
It is acidic. Rx with carbonate to give CO2 and with metals to give H2 (g).
NaOH (aq) to Cr3+ -> grey green ppt formed, dissolved in excess NaOH (aq) to give dark green solution.
Ligand exchange reaction between excess Cl- (aq) and copper (II) solution? What forms?
YELLOW COMPLEX of [CuCl4]2-
Addition of I- (aq) to copper (II) solution results in?
Redox reaction
2Cu2+(aq) + 4I- (aq) -> 2CuI (s) + I2 (aq)
The CuI is the off-white ppt, I2 is the brown solution.
A transition element is a ____________ element which forms ______________ stable simple ion in which there is a ________-_______ d subshell.
D-block
At least one
Partially-filled
Chromium transition metal
Ion of chromium (aq)??
[Cr(H2O)6]^3+ (aq)
NaOH (aq) added to chromium (III) solution!!
What colour is first formed? Give eqn.
Dissolves in excess NaOH (aq) to give what colour?? Give eqn.
Grey-green ppt : [Cr(H2O)6]3+ (aq) + 3OH- (aq) -> 👉🏻Cr(OH)3 (s)👈🏻 + 6H2O (l)
👉🏻Cr(OH)3 (s) 👈🏻+ 3OH- (aq) (reversible) [Cr(OH)6]3- (aq)
Yellow CrO4^2- (aq) and orange Cr2O7^2- (aq) can be converted to each other depending on pH of solution. Give EQNs.
Yellow CrO4^2-: need acid to convert to orange
2CrO4^2- (aq) + 2H+ (aq) Cr2O7^2- (aq) + H2O (l)
Orange need alkaline to convert to yellow
Cr2O7^2- (aq) + 2OH- (aq) 2CrO4^2- (aq) + H2O (l)
What colour is Mn2+ (aq)?
Pink / colourless
MnO4- is what colour?
Purple
MnO4- reduced under slightly alkaline conditions to give MnO2 (s) which is what colour?
Dark brown.
Aqueous fe3+ ion is acidic. True / false?
TRUE, [Fe(H2O)6]^3+ is acidic, reacts with carbonates to give carbon dioxide and metals to give hydrogen gas.
Equation to show that it is acidic:
[Fe(H2O)6]^3+ + H2O (l) [Fe(H2O)5(OH)]2+ (aq) + H3O+ (aq)
Which is stronger and more stable, polydentate or monodentate ligands?
Polydentate -> more coordinate / dative bonds, can hold on to central metal atom/ion better -> more stable.
When NaOH(aq) added to Fe2+ solution what happens? What ppt formed? What happens if it is left in the air?
[Fe(H2O)6]^2+ (aq) + 2OH- (aq) -> Fe(OH)2 (s) + 6H2O (l)
A GREEN ppt is formed (red light absorbed). Upon leaving in air, green ppt turns reddish brown.
4Fe(OH)2 + O2 + 2H2O -> 4Fe(OH)3 (green ppt is oxidised, Fe2+ to Fe3+)
CN- added to Fe2+ solution -> what occurs?
Ligand exchange reaction.
[Fe(H2O)6]2+ (aq) + 6CN- (aq) [Fe(CN)6]^4- (aq) + 6H2O (l)
SCN- (aq) added to Fe3+ solution -> what occurs?
Ligand exchange reaction.
[Fe(H2O)6]3+ (aq) + SCN- (aq) [Fe(SCN)(H2O)5]^2+ (aq) + H2O (l) (blood red complex formed) 😡
What colour is copper solid?
💞💞💞💞💞💞💞💞💞 PINK 💞💞💞💞💞💞💞💞
Copper (II) Cu2+ salts dissolve in water to give what solutions? what colour?
💎💎💎 BLUE 💎💎💎 SOLUTIONS!!!!!!!!!!
What ion is formed? [Cu(H2O)6]2+ (aq)
When NH3 (aq) is added to the [Cu(H2O)6]2+ (aq) what is formed initially? In excess?
First derive your OH- ions from NH3 dissolved in water:
NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)
Then realise that the [Cu(H2O)6]2+ (aq) react with the OH-!!
A 💎💎💎 BLUE 💎💎💎 precipitate of Cu(OH)2 is formed.
[Cu(H2O)6]^2+ (aq) + 2OH- (aq) -> Cu(OH)2 (s) + 6H2O (l)
Upon excess NH3 (aq), precipitate DISSOLVES, gives 💙💙dark blue 💙💙 solution.
Cu(OH)2 (s) + 4NH3 (aq) + 2H2O (l) [Cu(NH3)4(H2O)2]^2+ (aq) + 2OH- (aq)
Addition of excess Cl- (aq) to copper (II) solution results in what reaction? Formation of?
LIGAND EXCHANGE REACTION.
[CuCl4]^2- (aq) formed is 💛 yellow 💛 complex.
[Cu(H2O)6]^2+ (Aq) + 4Cl- (aq) [CuCl4]^2- (aq) + 6H2O (l)
Addition of I- (aq) to copper (II) solution results in what reaction? What ppt? What OBSERVATIONS?
Redox reaction! Our FAVOURITE because it benefits one at the cost of another! 🌝
2Cu2+ (aq) + 4Cl- (aq) -> 2CuI (s) + I2 (aq)
CuI (haha, cui sia) is an 🐑 off-white🐑 ppt (because Cu+ is not transition element anymore), I2 is 🍩 brown 🍩 solution.
What are the complementary colours!
🌹 Red - Green 🌵 (christmas)
💙 Blue - Orange 🎃 (poqing)
💛 Yellow - Purple 💜(happiness)
When Cl- (aq) added to silver (I) Ag+ solution, what is formed? Dissolves in NH3 (aq) to give?
Ag+ (aq) + Cl- (aq) -> AgCl (s) which is white ppt
Ppt dissolves in NH3 (aq) to give colourless solution
AgCl (s) + 2NH3 (aq) [Ag(NH3)2]+ + Cl- (aq)
