Inorganic Chemistry: D and F Blocks PDF

Inorganic Chemistry : D Block and F Block Part 1) D Block ​ Zinc, cadmium and mercury of group 12 have full d 10 configuration in their ground state as well as in their common oxidation states and hence, are not regarded as transition metals ​ In general the electronic configuration of o...

Inorganic Chemistry : D Block and F Block Part 1) D Block ​ Zinc, cadmium and mercury of group 12 have full d 10 configuration in their ground state as well as in their common oxidation states and hence, are not regarded as transition metals ​ In general the electronic configuration of outer orbitals of these elements is (n-1)d 1– 10 ns 1–2 except for Pd where its electronic configuration is 4d 105s 0 ​ The d orbitals of the transition elements protrude to the periphery of an atom more than the other orbitals (i.e., s and p), hence, they are more influenced by the surroundings as well as affect the atoms or molecules surrounding them. ​ elements exhibit certain characteristic properties such as display of a variety of oxidation states, formation of coloured ions and entering into complex formation with a variety of ligands. ​ The transition metals and their compounds also exhibit catalytic property and paramagnetic behaviour ​ bcc = body centred cubic; hcp = hexagonal close packed; ccp = cubic close packed; X = a typical metal structure ​ The transition metals (with the exception of Zn, Cd and Hg) are very hard and have low volatility. ​ In general, greater the number of valence electrons, stronger is the resultant bonding. ​ metals with very high enthalpy of atomisation (i.e., very high boiling point) tend to be noble in their reactions ​ metals of the second and third series have greater enthalpies of atomisation than the corresponding elements of the first series ​ There is the occurrence of much more frequent metal – metal bonding in compounds of the heavy transition metals. ​ Radius shows an increase from the first (3d) to the second (4d) series of the elements but the radii of the third (5d) series are virtually the same as those of the corresponding members of the second series ​ The filling of 4f before 5d orbital results in a regular decrease in atomic radii called Lanthanoid contraction ​ The net result of the lanthanoid contraction is that the second and the third d series exhibit similar radii (e.g., Zr 160 pm, Hf 159 pm) and have very similar physical and chemical properties ​ the shielding of one 4f electron by another is less than that of one d electron by another ​ The decrease in metallic radius coupled with increase in atomic mass results in a general increase in the density of these elements. ​ There is an increase in ionisation enthalpy along each series of the transition elements from left to right due to an increase in nuclear charge ​ the successive enthalpies of these elements do not increase as steeply as in the case of non-transition elements ​ The variation in ionisation enthalpy along a series of transition elements is much less in comparison to the variation along a period of non-transition elements ​ 3d electrons shield the 4s electrons from the increasing nuclear charge somewhat more effectively than the outer shell electrons can shield one another. Therefore, the atomic radii decrease less rapidly. ​ Thus also ionization energies increase only slightly along the 3d series. ​ one d electron does not shield another electron from the influence of nuclear charge because d-orbitals differ in direction. ​ Exchange energy is responsible for the stabilisation of energy state. ​ Exchange energy is approximately proportional to the total number of possible pairs of parallel spins in the degenerate orbitals ​ When several electrons occupy a set of degenerate orbitals, the lowest energy state corresponds to the maximum possible extent of single occupation of orbital and parallel spins. ​ The loss of exchange energy increases the stability. As the stability increases, the ionisation becomes more difficult ​ the second ionisation enthalpy which shows unusually high values for Cr and Cu where M + ions have the d 5 and d 10 configurations respectively. ​ The value for second enthalpy of Zn is correspondingly low as the ionisation causes the removal of one 4s electron which results in the formation of stable d 10 configuration. ​ the high values for third ionisation enthalpies of copper, nickel and zinc indicate why it is difficult to obtain oxidation state greater than two for these elements ​ Order of IE : 1st Sc V Cr Ti Mn Ni Cu Co Fe Zn Sakshi Varma Kar Ti Manmani Nahi Cutte Ko Fekne Jati ​ The elements which give the greatest number of oxidation states occur in or near the middle of the series. Manganese, for example, exhibits all the oxidation states from +2 to +7 ​ The lesser number of oxidation states at the extreme ends stems from either too few electrons to lose or share or too many d electrons ​ The maximum oxidation states of reasonable stability correspond in value to the sum of the s and d electrons upto manganese ​ This is followed by a rather abrupt decrease in stability of higher oxidation states ​ The variability of oxidation states, a characteristic of transition elements, arises out of incomplete filling of d orbitals in such a way that their oxidation states differ from each other by unity ​ Although in the p–block the lower oxidation states are favoured by the heavier members (due to inert pair effect), the opposite is true in the groups of d-block ​ Mo(VI) and W(VI) are found to be more stable than Cr(VI). ​ Higher os are favoured by heavier metals in d block ​ Low oxidation states are found when a complex compound has ligands capable of π-acceptor character in addition to the σ-bonding. ​ Ni(CO)4 and Fe(CO)5 , the oxidation state of nickel and iron is zero ​ Most stable OS: Sc Ti V Cr Mn Fe Co Ni Cu Zn 3 4 5 6, 3 7, 2 2,3 2,3 2 2 2 ​ Fe does not show +5 and Sc does not show +2 ​ +1 is shown by copper only ​ The unique behaviour of Cu, having a positive E V , accounts for its inability to liberate H2 from acids. ​ Only oxidising acids (nitric and hot concentrated sulphuric) react with Cu, the acids being reduced  ​ The high energy to transform Cu(s) to Cu2+(aq) is not balanced by its hydration enthalpy. ​ the value of E V for Mn, Ni and Zn are more negative than expected from the trend. ​ The stability of the half-filled d sub-shell in Mn2+ and the completely filled d 10 configuration in Zn2+ are related to their E V values, whereas E V for Ni is related to the highest negative ∆hydH V ​ Order of M2+ —-> M : Sc Ti V* Mn* Cr Zn Fe Co Ni Cu – Tiwari varma mange car zanab fir coi nai kyu? ​ Sc has very unstable ​ Value of V and Mn is same ​ Table goes negative to positive (Cu only) ​ Order of M3+ —> M2+ Sc Cr (-) Ti(-) V(-) Fe(+) Mn(+) Co(+) Ni Cu Zn – Kar Ti Vo Firse Man ka – – – ​ Sc has very unstable 2+ ​ Cu, Ni, Zn have very stable 2+ ​ Table goes -ve to positive ​ The highest value for Zn is due to the removal of an electron from the stable d 10 configuration of Zn2+ ​ The comparatively low value for V is related to the relative stability of V2+ ​ The +7 state for Mn is not represented in simple halides (Max = MnF4) ​ The highest oxidation numbers are achieved in TiX4 (tetrahalides), VF5 and CrF6 ​ MnO3F is known, and beyond Mn no metal has a trihalide except FeX3 and CoF3 ​ The ability of fluorine to stabilise the highest oxidation state is due to either higher lattice energy as in the case of CoF3 , or higher bond enthalpy terms for the higher covalent compounds, e.g., VF5 and CrF6. ​ Although V+5 is represented only by VF5, the other halides, however, undergo hydrolysis to give oxohalides, VOX3. ​ Another feature of fluorides is their instability in the low oxidation states e.g., VX2 (X = CI, Br or I) ​ all Cu(II) halides are known except the iodide. In this case, Cu2+ oxidises I– to I2 ​ many copper (I) compounds are unstable in aqueous solution and undergo disproportionation. ​ The stability of Cu2+ (aq) rather than Cu+ (aq) is due to the much more negative ∆hydH V of Cu2+ (aq) than Cu+ , which more than compensates for the second ionisation enthalpy of Cu. ​ The ability of oxygen to stabilise the highest oxidation state is demonstrated in the oxides. ​ No higher oxides of Fe above Fe2O3 , are known, although ferrates (VI) (FeO4 )2–, are formed in alkaline media but they readily decompose to Fe2O3 and O2. ​ The ability of oxygen to stabilise these high oxidation states exceeds that of fluorine ​ oxocations stabilise V (V) as VO2 + , V (IV) as VO2+ and Ti (IV) as TiO2+ ​ The ability of oxygen to form multiple bonds to metals explains its superiority. ​ The tetrahedral [MO4 ]n- ions are known for V(V) , CrVl, MnV , MnVl and MnVII. ​ In the covalent oxide Mn2O7 , each Mn is tetrahedrally surrounded by O’s including a Mn–O–Mn bridge ​ The metals of the first series with the exception of copper are relatively more reactive and are oxidised by 1M H+ , though the actual rate at which these metals react with oxidising agents like hydrogen ion (H+ ) is sometimes slow ​ An examination of the E V values for the redox couple M3+/M2+ shows that Mn3+ and Co3+ ions are the strongest oxidising agents in aqueous solutions ​ The ions Ti 2+, V2+ and Cr2+ are strong reducing agents and will liberate hydrogen from a dilute acid ​ Diamagnetic substances are repelled by the applied field while the paramagnetic substances are attracted ​ Substances attracted very strongly are said to be ferromagnetic. In fact, ferromagnetism is an extreme form of paramagnetism.  ​ Paramagnetism arises from the presence of unpaired electrons, each such electron having a magnetic moment associated with its spin angular momentum and orbital angular momentum ​ For first series of transition metals, the contribution of the orbital angular momentum is effectively quenched and hence is of no significance. ​ The colour observed corresponds to the complementary colour of the light absorbed ​ The frequency of the light absorbed is determined by the nature of the ligand ​ In aqueous solutions where water molecules are the ligands, the colours of the ions observed are Sc(2+) Ti(2+) V(2+) Cr(2+) Mn(2+) Fe(2+) Co(2+) Ni(2+) Cu(2+) Zn(2+) – – Violet Blue Pink Green Bluepink Green Blue Coless Very Beauti Pretty Girl Pinky Go Bank Colony ful Sc(3+) Ti(3+) V(3+) Cr(3+) Mn(3+) Fe(3+) Co(3+) Ni(3+) Cu(3+) Zn(3+) Coless Purpl Gren violet violet yellow Blupink – – – Cool Pretty Girl Vinni Very Young Behold ​ Ti(4+) is colorless ​ The transition metals form a large number of complex compounds. This is due to the comparatively smaller sizes of the metal ions, their high ionic charges and the availability of d orbitals for bond formation. ​ the transition metals and their compounds are known for their catalytic activity. This activity is ascribed to their ability to adopt multiple oxidation states and to form complexes ​ Vanadium(V) oxide (in Contact Process), finely divided iron (in Haber’s Process), and nickel (in Catalytic Hydrogenation) are some of the examples ​ Catalysts at a solid surface involve the formation of bonds between reactant molecules and atoms of the surface of the catalyst ​ This has the effect of increasing the concentration of the reactants at the catalyst surface and also weakening of the bonds in the reacting molecules (the activation energy is lowering) ​ because the transition metal ions can change their oxidation states, they become more effective as catalysts. ​ Interstitial compounds are those which are formed when small atoms like H, C or N are trapped inside the crystal lattices of metals. ​ They are usually non stoichiometric and are neither typically ionic nor covalent. ​ for example, TiC, Mn4N, Fe3H, VH0.56 and TiH1.7 ​ They have high melting points, higher than those of pure metals ​ they are very hard, some borides approach diamond in hardness ​ They retain metallic conductivity ​ They are chemically inert. ​ Alloys may be homogeneous solid solutions in which the atoms of one metal are distributed randomly among the atoms of the other ​ Such alloys are formed by atoms with metallic radii that are within about 15 percent of each other ​ The alloys so formed are hard and have often high melting points ​ the best known are ferrous alloys: chromium, vanadium, tungsten, molybdenum and manganese are used for the production of a variety of steels and stainless steel. ​ Alloys of transition metals with non transition metals such as brass (copper-zinc) and bronze (copper-tin), are also of considerable industrial importance. ​ All the metals except scandium form MO oxides which are ionic ​ As the oxidation number of a metal increases, ionic character decreases. ​ In the case of Mn, Mn2O7 is a covalent green oil ​ Even CrO3 and V2O5 have low melting points ​ In these higher oxides, the acidic character is predominant ​ Mn2O7 gives HMnO4 and CrO3 gives H2CrO4 and H2Cr2O7. ​ V2O5 is, however, amphoteric though mainly acidic and it gives VO4 3– as well as VO2 + salts. ​ In vanadium there is gradual change from the basic V2O3 to less basic V2O4 and to amphoteric V2O5 ​ V2O4 dissolves in acids to give VO2+ salts ​ V2O5 reacts with alkalis as well as acids to give VO4 3− and VO4 + respectively ​ The well characterised CrO is basic but Cr2O3 is amphoteric. ​ Potassium dichromate is a very important chemical used in leather industry and as an oxidant for preparation of many azo compounds. ​ Dichromates are generally prepared from chromate, which in turn are obtained by the fusion of chromite ore (FeCr2O4 ) with sodium or potassium carbonate in free access of air ​ The yellow solution of sodium chromate is filtered and acidified with sulphuric acid to give a solution from which orange sodium dichromate, Na2Cr2O7. 2H2O can be crystallised. ​ Sodium dichromate is more soluble than potassium dichromate ​ The latter(last one) is therefore, prepared by treating the solution of sodium dichromate with potassium chloride. ​ The chromates and dichromates are interconvertible in aqueous solution depending upon pH of the solution ​ Chromate + Acid —> Dichromate ​ Dichromate + Base —> Chromate ​ the dichromate ion consists of two tetrahedra sharing one corner with Cr–O–Cr bond angle of 126 ​ dichromates are strong oxidising agents ​ the sodium salt has a greater solubility in water and is extensively used as an oxidising agent in organic chemistry. ​ Potassium dichromate is used as a primary standard in volumetric analysis ​ Potassium permanganate is prepared by fusion of MnO2 with an alkali metal hydroxide and an oxidising agent like KNO3. ​ This produces the dark green K2MnO4 (manganate) which disproportionates in a neutral or acidic solution to give permanganate. ​ Commercially it is prepared by the alkaline oxidative fusion of MnO2 followed by the electrolytic oxidation of manganate. ​ a manganese (II) ion salt is oxidised by peroxodisulphate to permanganate. ​ Potassium permanganate forms dark purple (almost black) crystals which are isostructural with those of KClO4. ​ The salt is not very soluble in water ​ when heated it decomposes at 513 K to Manganate and MnO2 ​ It has temperature dependent weak paramagnetism ​ Potassium permanganate is used as a favourite oxidant in preparative organic chemistry. ​ Its uses for the bleaching of wool, cotton, silk and other textile fibres and for the decolourisation of oils are also dependent on its strong oxidising power. Part 2) F-Block ​ Lanthanum and Actinium are not part of F-Block, but still used in comparison as their properties match a lot with lanthanoids and actinoids. ​ The lanthanoids resemble one another more closely than do the members of ordinary transition elements in any series. ​ The chemistry of the actinoids is, on the other hand, much more complicated. The complication arises partly owing to the occurrence of a wide range of oxidation states in these elements ​ In Lanthanoids the electronic configurations of all the tripositive ions (the most stable oxidation state of all the lanthanoids) are of the form 4f n (n = 1 to 14 with increasing atomic number). ​ The overall decrease in atomic and ionic radii from lanthanum to lutetium (the lanthanoid contraction) is a unique feature in the chemistry of the lanthanoids ​ The shielding of one 4 f electron by another is less than one d electron by another with the increase in nuclear charge along the series. ​ The almost identical radii of Zr (160 pm) and Hf (159 pm), a consequence of the lanthanoid contraction, account for their occurrence together in nature and for the difficulty faced in their separation. ​ Ln(III) compounds are predominant species. However, occasionally +2 and +4 ions in solution or in solid compounds are also obtained. ​ This irregularity (as in ionisation enthalpies) arises mainly from the extra stability of empty, half-filled or filled f subshell ​ the formation of Ce(IV) is favoured by its noble gas configuration, but it is a strong oxidant reverting to the common +3 state. ​ Ce(IV) is a good analytical reagent ​ Pr, Nd, Tb and Dy also exhibit +4 state but only in oxides, MO2. ​ Eu2+ is formed by losing the two s electrons and its f 7 configuration accounts for the formation of this ion ​ Eu2+ is a strong reducing agent changing to the common +3 state ​ Similarly Yb2+ which has f 14 configuration is a reductant ​ TbIV has half-filled f-orbitals and is an oxidant ​ The behaviour of samarium is very much like europium, exhibiting both +2 and +3 oxidation states. Ce Pr Nd Pm Sm Eu Gd 4f 1 5d1 4f 3 4f 4 4f 5 4f 6 4f 7 4f 7 5d1 Tb Dy Ho Er Tm Yb Lu 4f 9 4f 10 4f 11 4f 12 4f 13 4f 14 4f14 5d1 ​ All of these have a 6s2 at the end (omitted in the table) ​ Ce 2+ shows 4f 2 config ​ 4+ OS is shown by Ce, Pr, Nd, Tb and Dy only ​ All the lanthanoids are silvery white soft metals and tarnish rapidly in air ​ The hardness increases with increasing atomic number, samarium being steel hard. ​ Their melting points range between 1000 to 1200 K but samarium melts at 1623 K ​ Many trivalent lanthanoid ions are coloured both in the solid state and in aqueous solutions. Colour of these ions may be attributed to the presence of f electrons. ​ Neither La3+ nor Lu3+ ion shows any colour but the rest do so ​ absorption bands are narrow, probably because of the excitation within f level ​ The lanthanoid ions other than the f 0 type (La3+ and Ce4+) and the f 14 type (Yb2+ and Lu3+) are all paramagnetic. ​ the earlier members of the series are quite reactive similar to calcium but, with increasing atomic number, they behave more like aluminium ​ The metals combine with hydrogen when gently heated in the gas ​ The carbides, Ln3C, Ln2C3 and LnC2 are formed when the metals are heated with carbon ​ They liberate hydrogen from dilute acids ​ burn in halogens to form halides ​ They form oxides M2O3 and hydroxides M(OH)3. ​ The hydroxides are definite compounds, not just hydrated oxides ​ The best single use of the lanthanoids is for the production of alloy steels for plates and pipes ​ A well known alloy is mischmetall which consists of a lanthanoid metal (~ 95%) and iron (~ 5%) and traces of S, C, Ca and Al. ​ A good deal of mischmetall is used in Mg-based alloy to produce bullets, shell and lighter flint.  ​ Mixed oxides of lanthanoids are employed as catalysts in petroleum cracking. ​ Some individual Ln oxides are used as phosphors in television screens and similar fluorescing surfaces. ​ The actinoids are radioactive elements and the earlier members have relatively long half-lives, the latter ones have half-life values ranging from a day to 3 minutes for lawrencium (Z =103) ​ All the actinoids are believed to have the electronic configuration of 7s2 and variable occupancy of the 5f and 6d subshells. ​ The irregularities in the electronic configurations of the actinoids, like those in the lanthanoids are related to the stabilities of the f 0 , f 7 and f 14 occupancies of the 5f orbitals. ​ Although the 5f orbitals resemble the 4f orbitals in their angular part of the wave-function, they are not as buried as 4f orbitals and hence 5f electrons can participate in bonding to a far greater extent Th Pa U Np Pu Am Cm 6d2 5f 2 6d1 5f 3 6d1 5f 4 6d 1 5f 6 5f 7 5f 7 6d1 Bk Cf Es Fm Md No Lr 5f 9 5f 10 5f 11 5f 12 5f 13 5f 14 5f14 6d1 ​ The fourteen electrons are formally added to 5f, though not in thorium (Z = 90) but from Pa onwards the 5f orbitals are complete at element 103. ​ There is a gradual decrease in the size of atoms or M3+ ions across the series. This may be referred to as the actinoid contraction ​ The contraction is greater from element to element in this series resulting from poor shielding by 5f electrons. ​ There is a greater range of oxidation states, which is in part attributed to the fact that the 5f, 6d and 7s levels are of comparable energies. ​ The elements, in the first half of the series frequently exhibit higher oxidation states ​ General Os = 3+ ​ For example, the maximum oxidation state increases from +4 in Th to +5, +6 and +7 respectively in Pa, U and Np ​ The actinoids resemble the lanthanoids in having more compounds in +3 state than in the +4 state. ​ +3 and +4 ions tend to hydrolyse ​ it is unsatisfactory to review their chemistry in terms of oxidation states. because the distribution of oxidation states among the actinoids is so uneven ​ The actinoid metals are all silvery in appearance ​ They display a variety of structures. The structural variability is obtained due to irregularities in metallic radii ​ The actinoids are highly reactive metals, especially when finely divided. ​ The action of boiling water on them, for example, gives a mixture of oxide and hydride and combination with most non metals takes place at moderate temperatures ​ Hydrochloric acid attacks all metals but most are slightly affected by nitric acid owing to the formation of protective oxide layers ​ alkalies have no action on actinoids ​ The magnetic properties of the actinoids are more complex than those of the lanthanoids ​ the ionisation enthalpies of the early actinoids, though not accurately known, but are lower than for the early lanthanoids ​ This is quite reasonable since it is to be expected that when 5f orbitals are beginning to be occupied, they will penetrate less into the inner core of electrons. ​ The 5f electrons, will therefore, be more effectively shielded from the nuclear charge than the 4f electrons of the corresponding lanthanoids ​ Because the outer electrons are less firmly held, they are available for bonding in the actinoids ​ even the early actinoids resemble the lanthanoids in showing close similarities with each other and in gradual variation in properties which do not entail change in oxidation state. ​ TiO for the pigment industry and MnO2 for use in dry battery cells ​ The battery industry also requires Zn and Ni/Cd ​ The elements of Group 11 are still worthy of being called the coinage metals. ​ the contemporary UK ‘copper’ coins are copper-coated steel. The ‘silver’ UK coins are a Cu/Ni alloy ​ V2O5 catalyses the oxidation of SO2 in the manufacture of sulphuric acid ​ TiCl4 with A1(CH3 )3 forms the basis of the Ziegler catalysts used to manufacture polyethylene (polythene) ​ Iron catalysts are used in the Haber process for the production of ammonia  ​ Nickel catalysts enable the hydrogenation of fats to proceed ​ In the Wacker process the oxidation of ethyne to ethanal is catalysed by PdCl2 ​ Nickel complexes are useful in the polymerisation of alkynes and other organic compounds such as benzene. ​ The photographic industry relies on the special light-sensitive properties of AgBr. Part 3) NCERT Tables Order of Metallic radii Co* Ni* Fe Cu Cr V Mn** Zn** Ti Sc ​ Values of Co Ni are same ​ Values of Mn Zn are same Order of Mp Zn Cu Mn Ni Co Fe Sc Ti Cr V