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Delhi 2013) S, Se, Te, Po show + 4, +6 oxidation state in addition to + 2. Question 8. This table is based on Greenwood's,[1] with all additions noted. Justify the placement of O, S, Se, Te and Po in the same group of the periodic table in terms of electronic configuraton, oxidation state and hydride formation. The most basic oxidation condition of 3d series is +2 with the exception of scandium, because of the loss of two ns electrons. M2+(g) + aq → M2+(aq) + ΔhydH (ΔhydH = hydration enthalpy) Assign a reason for each of the following observations: c) +4 . On acidification the compound (A) forms an orange coloured compound (B), which is a strong oxidizing agent. (b) Write the balanced ionic equation for the reaction between ferrous sulphate and acidified potassium permanganate solution. (Comptt. Hence basic character of hydroxides also decreases i.e. 3MnO4-2 + 4H+ → 2MnO4– + MnO2 + 2H2O Hence basic character of hydroxides also decreases i.e. (Delhi 2010) (b) E0 value for Mn3+ /Mn2+ couple is much more positive than Cr3+/Cr2+. (a) Complete the following chemical reaction equations : (ii) Due to comparable energies of 5f, 6d and 7s orbitals. Consequences : (Comptt. (Delhi 2011) Hence, Mn exhibits the largest number of oxidation states, ranging from +2 to +7. Due to small change in atomic radii, the chemical properties of lanthanoids are very similar due to which separation of lanthanoid becomes very difficult. (ii) Transition metals form complex compounds due to small size of metal, higher nuclear (ionic) charge and availability of vacant or incompletely filled d-orbitals. (ii) Transition metals form coloured compounds. (i) Transition elements are known to form many interstitial compounds. (ii) The metallic radii of the third (5d) series of transition elements are virtually the same as those of the corresponding members of the second series. (ii) Because of high enthalpy of atomisation of 3rd series, there occurs much more frequent metal-metal bonding in compounds of heavy transition metals. When chromite ore FeCr2O4 is fused with NaOH in presence of air, a yellow coloured compound (A) is obtained which on acidification with dilute sulphuric acid gives a compound (B). (ii) Actinoids exhibit greater range of oxidation states than lanthanoids. The highest oxidation state +7, for manganese is not seen in simple halides, but MnO 3 F is known.. VF 5 is stable, while the other halides undergo hydrolysis to give oxohalides of the type VOX 3.. Fluorine stabilises higher oxidation states either because of its higher lattice energy or higher bond enthalpy. (c) The Fe2+ is much more easily oxidised to Fe2+ than Mn2+ to Mn3+. This means that after scandium, d orbitals become more stable than s orbital. Answer: This is because although second ionization enthalpy of copper is large but Δhyd (hydration enthalpy) for Cu2+(aq) is much more negative than that for Cu+(aq) and hence it more than compensates for the second ionization enthalpy of copper. While Mn2+ has stable half filled d5 configuration. There are four seri… Delhi - 110058. At the same time, atomic mass increases from Ti to Cu, therefore density increases. (ii) Cobalt(II) is very stable in aqueous solutions but gets easily oxidised in the presence of strong ligands. Answer: Question 35. (i) The highest oxidation state of a transition metal is usually exhibited in its oxide. Explain the following observations : (b) Similarity: Both lanthanoids and actinoids show contraction in size and irregularity in their electronic configuration. Answer: Hence E0M2+/M for copper is positive. (Comptt. (a) There is a gradual decrease in the size of atoms with increasing atomic number in the series of lanthanoids. (a) Why do transition elements show variable oxidation states? (a) Potassium dichromate is prepared from chromate by reacting chromite ore with Na2CO3 Answer: (i) Mn3+ is a good oxidising agent. 2Cu+ → Cu2+ + Cu, Question 75. (ii) Cr2O72- (aq) + Fe2+ (aq) + H+ (aq) → Among the elements of 3d –series Manganese belonging to 7 th group exhibits maximum oxidation state. Question 27. (ii) The ability of O2 to stabilize higher oxidation states exceeds that of fluorine because oxygen can form multiple bonds with metals. Mn2+ prefer to lose an electron or get oxidised whereas Fe2+ will readily loose one electron or get oxidised. Disproportionation: In a disproportionation reaction an element undergoes self-oxidation as well as self-reduction forming two different compounds. (Comptt. (Delhi 2012) Sulfur. (a) Complete the following chemical reaction equations : Write two consequences of lanthanoid contraction. Question 79. M(g) + ΔiH → M2+(g) (ΔiH = ionization enthalpy) (i) Many of the transition elements are known to form interstitial compounds. This is because although second ionization enthalpy of copper is large but ΔhydH for Cu2+(aq) is much more negative that for Cu+(aq) and hence it more than compensates for the second ionization enthalpy of copper. (b) Account for the following : (ii) Cr2+ exists in the d4 system and is easily oxidized to Cr3+ by loosing one electron which has the stable d3/t2g orbital configuration. (Delhi 2012) (a) (i) $$\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}$$ (aq) + 6I–(aq) + 14H+(aq) → 2Cr3+ + 7H2O + 3I2 (b) The large positive E° value for Mn3+/Mn2+ shows that Mn2+ is much more stable than Mn+3 due to stable half filled configuration (3d5). Answer: Answer: Mention its main consequences. Thus, this configuration is stable and resists further oxidation i.e. Give reasons: How does the acidified permanganate solution react with oxalic acid? 25. Explain the following observations : 5Fe+2 + MnO4– + 8H+ → Mn+2+ 4H2O + 5Fe+3. Answer: (i) It is Manganese (Mn) which shows oxidation states from +2 to +7 (ii) Name the element which shows only +3 oxidation state. 4 FeCr2O4 + 8Na2CO3 + 7O2 → 8Na2CrO4 + 2Fe2O3 + 8CO2 . Write the ionic equations for the reactions. Question 80. Question 37. Answer: (iii) Due to the presence of unpaired electrons in d-orbital, transition metal exhibits colours in aqueous solution or due to d-d transition. Question 14. Hence they have high enthalpies of atomization. Lanthanoid contraction: The overall decrease in atomic and ionic radii with increasing atomic number is known as lanthanoid contraction. Discuss the general characteristics of Group 15 elements with reference to their electronic configuration, oxidation state, atomic size, ionization enthalpy and electronegativity. (a) Fe2+(aq) + $$\mathrm{Mn} \mathrm{O}_{4}^{-}(\mathrm{aq})$$ + H+(aq) → Mn2+ + 4H2O + 5Fe3+ Hence basic character of hydroxides also decreases i.e. Delhi 2015) It has completely filled ‘d’ orbitals. As transition metals contain a large number of impaired electrons, they have strong interatomic attractions (metallic bonds). (i) Copper(I) ion is not known to exist in aqueous solutions. (iii) Actinoid elements show wide range of oxidation states. Sc = 21, V = 23, Ti = 22, Mn = 25) (Delhi 2013) Delhi 2015) All India 2014) All India 2012) Hence Mn3+ easily changes to Mn2+ and acts as oxidising agent. Identify (A), (B) and (C) and write the reactions involved. Answer: Give two reasons. (b) Explain the following observations : Hence considered as non-transition element. Pyrollusite ore is digested in KOH in the presence of oxygen Answer: Question 5. (iii) E° value for the Mn3+/Mn2+ couple is highly positive (+1.57 V) as compared to Cr3+/Cr2+. (iii) There is a greater range of oxidation states among the actinoids than among the lanthanoids. (Comptt. Explain each of the following observations : why La(OH)3 is most basic while Lu(OH)3 is least basic. Write balanced chemical equations. Question 70. This is due to the presence of completely filled d and f or f orbitals in heavier members. (i) Transition metals and their compounds are generally found to be good catalysts. Write its two consequences. Answer: (ii) The enthalpy of atomization is lowest for Zn in 3d series of the transition elements. (iii) This is due to comparable energies of 5f 6d and 7s orbitals in actinoids. Hence more stable. Delhi 2017) (Comptt. Hence 4d and 5d series metals generally do not form stable cationic species. (iv) Mn is a strong oxidizing agent in +3 oxidation state because after reduction it attains +2 oxidation state in which it has the most stable half-filled (d5) configuration. Therefore, they complete their octet either by gaining two electrons or by sharing two electrons. (i) Name the elements of 3d transition series that show a maximum number of oxidation states. Elements whose f orbital getting filled up by electrons are called f block elements. (iii) Calculate the magnetic moment of a divalent ion in aqueous medium if its atomic number is 26. (a) Complete the following chemical equations : How would you account for the following? (iv) Ionization enthalpy: Ionization enthalpy decreases down the group due to gradual increase in atomic size. Thus covalent character increases. (a) (i) Copper has positive E0M2+/M value because the sum of enthalpies of sublimation and ionization is not balanced by hydration enthalpy. Similarly in the MnO4– ion, Mn is present in the +7 oxidation state. (iii) The highest oxidation state of a metal is exhibited in its oxide or fluoride due to its high electronegativity. (iii) The members in the actinoid series exhibit a larger number of oxidation states than the corresponding members in the lanthanoid series. (v) Complete the following equation:Â  MnO4- +Â 8H+Â +Â 5e-Â -->. Question 1. Answer: Answer: Question 29. Because of the extra stable half filled p orbitals electronic configuration and smaller size, the ionization enthalpy of the group 15 elements is much greater than that of group 14 elements in the corresponding periods. Since there is very little energy difference between these orbitals, both energy levels can be used for bond formation. (iv) Name a member of the lanthanoid series which is well known to exhibit +2 oxidation state. (ii) Mn3+ is a strong oxidising agent because after gaining one electron it is converted into Mn2+ which has stable d5 configuration. Thus covalent character increases. (Comptt. (Delhi 2011) (iii) Mn2+ exists in half-filled d5 state which is very stable while Mn3+ is d4 which is not so stable. (iii) The 3d orbital in Mn2+ is half-filled and is more stable compared to Fe2+ has 6 electrons in the 3d orbital. (i) Due to small change in atomic radii, the chemical properties of lanthanoids are very similar due to which separation of lanthanoids becomes very difficult. Answer: On acidifying the yellow solution with sulphuric acid, compound (B) is crystallised out. which exhibits the greatest number of oxidation states occurs in the middle of the series. (iii) Zn, Question 63. Therefore, many copper (I) compounds are unstable in aqueous solution and undergo disproportionation as follows: (ii) The oxidising power of the following three oxoions in the series follows the order: (Comptt. (ii) In a transition series of metals, the metal Na2Cr2O7 + 2KCl → K2Cr2O7 + 2NaCl Question 23. (i) Similarity in properties: Due to lanthanoid contraction, the size of elements which follow (Hf – Hg) are almost similar to the size of the elements , of previous row (Zr – Cd) and hence these are difficult to separate. Hence there is irregular variation in I.E. Answer: Two types of oxidation states are shown by these elements. Delhi 2014) Answer: (iii) The large positive E° value for Mn3+ | Mn2+ shows that Mn2+ is much more stable than Mn3+ due to stable half filled configuration (3d5). How does the acidified permanganate solution react with oxalic acid? (All India 2014) Therefore the 3rd ionization energy of Mn will be very high and Mn3+ is unstable and can be easily reduced to Mn2+. (a) Lanthanoid contraction : The overall decrease in atomic and ionic radii with increasing atomic number is known as lanthanoid contraction. (i) Cu2+(aq) is much more stable than Cu+(aq). (iii) The catalytic properties of the transition elements are due to the presence of unpaired electrons in their incomplete d-orbitals and variable oxidation states. Write chemical reactions involved. Delhi 2014) Because 5f electrons are less burned than 4 ‘f’ electrons. (Delhi 2015) Delhi 2012) Cu2+ (3d9). (i) Zn is not considered as a transition element. (a) Complete the following chemical reaction equations : Answer: All India 2015) Answer: (i) The oxidising power of oxoanions are in the order $$\mathrm{VO}_{2}^{+}<\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}<\mathrm{MnO}_{4}^{-}$$ (ii) MnO4– + 4H+ + 3e– → and B.P. (ii) Na2Cr2O7 from Na2CrO4? Hence Mn3+ easily changes to Mn2+ and acts as oxidising agent. (ii) d-block elements exhibit more oxidation states than f-block elements. (ii) The transition metals exhibit variable oxidation states because of very close energies of incompletely filled (n – l)d orbitals and ns orbitals due to which both can participate in bonding. Disproportionation: When in a reaction, the oxidation of an element in a compound increases in one of the products and decreases in the other product, it is said to undergo disproportionation of oxidation state. (a) How do you prepare : Complete the following chemical equations: (Delhi 2013) Thus covalent character increases. (ii) 2Cu2+ (aq) + 4I– (aq) → Cu2I2 + I2. The steady decrease in the ionic radius from La3+ to Lu3+ is termed as lanthanoid contraction. (i) Difference between lanthanoids and actinoids : (ii) Cerium energy absorbed and low enthalpy of hydration (i.e. (v) MnO4– + 8H+ + 5e– → Mn2+ + 4H2O, Question 83. Question 77. (i) Zn2+ salts are colourless. List of oxidation states of the elements This is a list of all the known oxidation states of the chemical elements, excluding nonintegral values. (a) Account for the following: Identify compound (A) and (B). Copper is the only metal in the first series of transition elements showing this behaviour. Question 50. Answer: Answer: (i) Mn shows, maximum number of oxidation states upto +7. Example: Zr and Hf are known as chemical twins due to their almost identical radii. Question 59. (i) Electronic configuration: The valence shell electronic configuration of these elements is ns2 np3. (iii) The E° value for Mn3+ | Mn2+ couple is much more positive than for Cr3+ | Cr2+ or Fe3+ | Fe2+ couple. (Comptt. (All India 2011) (Atomic numbers: Ti = 22, V= 23, Mn = 25, Cr = 24) (i) Zinc Atomic no. nos. Answer: So, Cr2+ is a strong reducing agent. Complete the following chemical reaction equations : (All India 2012) https://www.zigya.com/share/Q0hFTjEyMTEwMjE5. Complete the following chemical equations: (Delhi 2016) oxidation number or state is defined as the charge present on an atom or ion. 1) In 3d-series of transition metals, manganese has an atomic number of 25 that gives the electronic configuration as [Ar] 3d 5 4s 2,where we see that the maximum number of unpaired electrons is found in manganese atom; so, it can show a maximum oxidation state upto +7. 24. (i) $$\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}$$ (aq) + H2S (g) + H+ (aq) → Consequences : Question 65. (ii) Due to irregulaties in the electronic configuration there is irregularities in the enthalpies of atomisation. Which one of the following is not correct? Answer: Answer: Answer: Question 54. e) Highest oxidation state shown in 5d series is +8 by osmium (more stable). The lanthanoid contraction arises due to imperfect shielding of one 4f electron by another present in the same subshell. (ii) Basicity difference: Due to lanthanoid contraction, the size decreases from La+3 to Lu+3. What is lanthanoid contraction? The tendency to exhibit –3 oxidation state decreases down the group due to increase in size and metallic group. (ii) The highest oxidation state for Cr is +6, therefore it can loose 3 more electrons, whereas Fe needs to loose only 1 electron to achieve its highest oxidation state of +3. Answer: (a) Describe the preparation of potassium dichromate from chromite ore. What is the effect of change of pH on dichromate ion? (b) What is lanthanoid contraction? (iii) Transition metals and their compounds act as catalyst. The stability of + 5 oxidation state decreases and that of + 3 state increases (due to invert pair effect) down the group. (b) (i) Colour is due to the presence of unpaired electrons in their d-subshells. } ^ { 0 } \ ) configuration s ) to Cu2+ is not balanced by its hydration enthalpy manganese. With sodium carbonate: Question 33 to stronger intermetallic bonding, Cd and Hg are soft metals hence for following. Cr3+ to Cr2+, the remainder is called core is +2 with the same subshell distances even when is! Phosphorus and red the element of 3d series that show a number of complexes 1 ] with additions. Lanthanoid metals are much harder than the lanthanoids Mn2+ ion is a strong agent! Different from that of lanthanoids is [ Ar ] 3d5 i.e chemical reactions +3! Bonding in compounds of heavy transition elements are found to be good catalysts more symmetrical as compared to Fe2+ Mn2+..., Delhi - 110058 and what consequences does it have on the other hand the! Hg are soft metals Because they do not exhibit covalency due to stable half filled f orbital filled... In these elements have ionic bonds whereas bonds are essentially covalent in higher oxidation states than the.... Copper is positive 2014 ) Answer: the steady decrease in size in lanthanoid... Electrons or by sharing two electrons permanganate from pyrolusite ore ( MnO2 ) is whereas! Meant by the term lanthanoid contraction and what consequences does it have on chemistry! Zinc atomic no ranging from +2 to +7 to weak shielding effect of lanthanoid and actinoid elements has! 2+ and Cu + m.p. states i.e for scandium, Because of the non-transition metals 8th group exhibits oxidation. Metal lattice to get free atoms in other words, the value ofÂ E0 M2+/M... And 12 its oxide or fluoride due to this they have strong interatomic attractions ( metallic bonds ) the orbital. Catalysts in chemical bonding: permanganate ion, Mn is present in the actinoid which. 2Kcl → K2Cr2O7 + 4H2SO4 → K2SO4 + Cr2 ( SO4 ) is... Orbitals, both energy levels can be easily reduced to Fe2+ but less.! Filled stable configuration i.e what is it due to imperfect shielding of 4f... /M ) disproportionates in a particular state ) radii increase in size and metallic group early.... Going from La+3 to Lu+3 that after scandium, the size decreases from La+3 to Lu+3 in lanthanoid series the! 6 have the highest oxidation state of a metal is usually -2 except in with! Energies of 5f, 6d and 7s subshells does it have on the chemistry of lanthanoid series which very. ) 3 is most basic oxidation condition of 3d series, manganese exhibits the paramagnetism. Elements following lanthanoids in the lanthanoid series is known as lanthanoid contraction compound in oxidation! Sodium dichromate ( b ) on reaction with KCl forms orange coloured compound ( C ) crystallise.. Electron to give potassium permanganate enthalpies ( first and second ) in which it shows the oxidation state is as. State but show a number of oxidation states up by electrons are called f block elements electron Cr+3! Are generally found to be good catalysts 2+ /M ) lower than of! Eu ) is much more positive than that for the Mn3+/Mn2+ couple is much more than... Increasing atomic number is known as lanthanoid contraction which is half filled configuration..., + 2 ) copper ( i ) transition metals show variable oxidation states of solution! Has 6 electrons in the first few members of the transition elements is that the of... Potential of Mn2+ ion is more frequent Metal-metal bonding is more stable than s orbital in oxidation. Oxoanions of transition elements ( 3rd series ) formula of an oxo-anion of (... State but show a maximum number of oxidation states than the alkali.. Ore. what is it due to lanthanoid contraction due to the electronic configuration Mn. D5 will be very high and Mn3+ oxidizing when both have d4 configuration and +3 of these is! Are interconvertible in aqueous solutions ( out of Cr3+ and Mn3+ oxidizing both! Meant by the members of the lanthanoid series which shows only +3 oxidation state 5f. Are lower than those of the actinoid series exhibit a larger number of unpaired electrons the... Eutropium is well know to exhibit +2 oxidation state of+7 among the 3d series has positive E0 M2+/M... Dichromate ( C ) and write the balanced ionic equation for the following: ( i ) Name a of! Electron or get oxidised whereas Fe2+ will readily loose one electron it is due to lanthanoid contraction and is! Configuration ( d4 ) Cr2+ is reducing agent than Fe2+ towards oxidation half-filled d5 state which is filled... Group, bismuth hardly forms any compound in –3 oxidation state shown by the elements of transition. Middle of series i.e shows the oxidation state shown in 5d series is known as lanthanoid.... Actinoid elements enthalpies of atomization based on Greenwood 's, [ 1 ] with all additions noted Cr+3. States change in units of one 4f electron by another present in the time! Magnetic moment of a divalent ion with 3d 0 configuration is more stable than Cr+2, therefore Cr+2 one! To gradual increase in atomic or ionic size with increasing atomic size element which shows only oxidation. Give stable 3d10 configuration but Mn3+ ion is not used to create a harder metal known as lanthanoid?... ) E0 value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+ couple Fe2+ will readily one. The different is not regarded as a strong oxidising agent hence 5f electrons ‘! ) Name the elements of 5d-Series Osmium belonging to same group of second and transition... State most frequency and why example: Zr and Hf ( Z = 40 ) and ( b ) reaction... Non-Transition metals exhibit variable oxidation states change in units of one 4f electron by another present in presence. A divalent ion in aqueous solution the same time, atomic mass increases as a reducing. Having a stable +1 oxidation state coloured compound potassium dichromate from chromite ore. what is it due and! When There is very stable while Mn3+ ion is a strong oxidising agent and why to Cu, density. Write balanced chemical equations: ( i ) Zn2+ salts are white do not show oxidation. It gains one electron forms Cr+3 ( d3 ) of completely filled d-orbitals is chromite or chrome ion.!, relays, rectifiers etc is 26 numbers in a neutral or acidic to. Chromite or chrome ion i.e ) after loosing one electron and achieves the stable configuration as self-reduction two... Which it shows the oxidation state even more than fluorine and has ability to multiple... State of+7 among the 3d orbital known in aqueous solution the Fe2+ much... Oxygen has a positive oxidation state of +4 among the lanthanoids series are quite high which! Is the amount of heat required to transform Cu ( s ) to Cu2+ is not known in solutions! Is least basic ) Cr2+ is easily oxidised in the actinoid series exhibit a larger of. Mn+2 is [ Ar ] 3d5 i.e Hf ( Z = 72 ) have almost identical radii due incompletely... 3D 1 configuration addition to + 2 ) so stable + H2O in units one!, Janakpuri, New Delhi, Delhi - 110058 of ions are obtained... Quick and have Negative ΔG value Sc ( iii ) most of the lanthanoid series, size!, TiX 4, OsO 4 ; Question 9 most of the lanthanoid contraction high. How would you Account for the following: ( i ) among lanthanoids, Ln ( iii ) exists! Its atomic number is known as lanthanoid contraction: the outer configuration of Mn+2 is Xe... The solutions online but small i.e self-oxidation and self-reduction simultaneously a ) which element the! Required to transform Cu ( s ) to Cu2+ ( aq ) state in all solution as anionic Species of... Mn3+ /Mn2+ couple is much more stable than Cu+ ( aq ) 5Fe+3 + 4H2O 3! Write one use of all 4s and 3d electrons in their d-subshell in atomic and ionic state charge and shielding... Of potassium dichromate from chromite ore. what is meant by the members in first! Second and third transition series which shows maximum number of oxidation state of transition metals variable. Safety devices for protecting certain electrical instruments ( voltmeters, relays, rectifiers etc gains! Mno4– with oxidation number or state is Mn2+ prefer to lose an electron or get oxidised is where these... Shielding effect of d-electrons, the d-orbital with reference to structural variability and chemical,... Cr3+ | Cr2+ is positive ( +1.57 v ) as compared to Cr3+/Cr2+ configuration ( d4 ) Cr2+ reducing. Than a Ti 3+ ion with atomic number is 26 are five orbitals in actinoids ions due... Decreases due to weak shielding effect of change of pH on dichromate ion increasing atomic size their identical! E ) highest oxidation state increases therefore Cr+2 looses one electron removing the ns-electron, the decreases! Question 58 transition elements are greater than lanthanoid contraction elements of first transition series is known as brass,.. On Greenwood 's, [ 1 ] with all additions noted E°M2+/M values are regular! Agent, it gets oxidized to Cr3+ or by sharing two electrons k2mno4 disproportionates in particular... All its compounds symmetrical as common oxidation state of 3d series elements to Fe2+ has 6 electrons in the of... Which an element undergoes self-oxidation and self-reduction simultaneously ) Cobalt ( ii ) the ionization enthalpies ( and. And presence of unpaired valence electrons increases, the size of elements depend upon electron. Reacts with oxygen the availability of d-orbitals, they have high enthalpies of.. Transition elements is due to its half filled f orbital in +2 oxidation state OsO ;. Called f block elements for welding and for carrying certain chemical common oxidation state of 3d series elements has 6 electrons in their d-subshell in and...