(b) (i) Refer Ans. Assign reasons for the following: (i) The atomic radii of the metals of the third (5d) series of transition elements are virtually the same as those of the corresponding members of the second (4d) series. Lanthanide oxidation states All of the lanthanide elements are commonly known to have the +3 oxidation state and it was thought that only samarium, europium, and ytterbium had the +2 oxidation readily accessible in solution. Answer: Actinoid contraction is greater from element to element than lanthanoid contraction. On the other hand Actinoids show a large number of oxidation states because of small energy gap between 5f, 6d and 7s subshell. (ii) Transition elements and their compounds are generally found to be good catalysts in chemical reactions. (i) Refer Ans. For any content/service related issues please contact on this number . • The lanthanoids have similar ionic size and resemble with each other closely in their properties. They have the ability to form complexes with ligands such as chlorides, sulfates, etc. (ii) E°CU2+/CU *ias +ve value due to high ionisation enthalpies and sublimation energies and lower hydration energy. (ii) There is a greater horizontal similarity in the properties of the transition elements than of the main group elements. The higher ionisation energies of the actinides tend to be smaller than those of the lanthanides, for the same reasons as explained in the linked question (5f orbitals have one radial node; 4f orbitals do not). Use: Its magnesium based alloy is used to produce bullets, shells, flints. (ii) Cr202– + H2S + H+ ———-> (ii) It is because all of them are radioactive and some of them have short half life, therefore, the chemistry of actinoids is not smooth. to Q.36 (ii). Lanthanoids show lanthanoid contraction like actinoids contraction. Answer: (i) Actinoid contraction is greater than lanthanoid contraction. Explain: Higher oxidation states are usually exhibited by the members in the middle of a series of transition elements. (v) Mn04 + 8H+ + 5e- ———> Mn2+ + 4H20. (iii) Refer Ans. (ii) Refer Ans. (iii) Transition metals and their compounds act as catalyst. Post author: Post published: December 2, 2020 Post category: Uncategorized Post comments: 0 Comments 0 Comments Question 60: (i) Transition metals exhibit variable oxidation states. (b) Account for the following: (b) (i) Refer Ans. In 3d series, ‘Mn’ shows maximum number of oxidation states because it has maximum number of electrons in s as well as in d orbitals which can take part in bond formation. However, there is a compensatory effect in that elements in higher oxidation states generally get more out of bonding. (iii)Transition metals show variable oxidation states. to Q.9 (ii). that means the ionization energy is lower for the corresponding oxidation state compared to lanthanides. (i) Fe2+ ions Question 36. (b) V3+ and Mn2+ are coloured, due to the presence of unpaired electrons, they can undergo d-d transitions. (ii) Oxidation state: Transition metals show variable oxidation states due to tendency of ‘d’ as well as ‘s’ electrons to take part in bond formation. Answer: The atomic size of Fe, Co, Ni is almost same because pairing of electrons takes place in rf-orbitals causing repulsion and effective nuclear charge does not increase appreciably. (iii) Zn has lowest enthalpy of atomisation. (i) There is in general an increase in density of element from titanium ‘ (Z = 22) to copper (Z = 29). So, which do you mean? Answer: (ii) There is a general increase in density from titanium (Z = 22) to copper (Z = 29). Why? Question 66: Iron has two common oxidation states (+2 and +3) in, for example, Fe 2+ and Fe 3+. Lanthanoids show limited oxidation states(+2,+3,+4). Explain each of the following observations: Though 3+ is the most stable oxidation state, other oxidation states are possible because of the good shielding of f-electrons. of Ce = 58] View Answer. (ii) KMn04 from K2MnO4 (ii) It is because Cu2+ is more stable because hydration energy overcomes 2nd ionisation energy. Account for the following: (iii) Refer Ans. How would you account for the following? (iii) Oxidation state : The most common oxidation state of lanthanoids is +3 while actinoids show more variable oxidation states than lanthanoids ranging from +3 to +7. Answer: Answer: The elements, in the first half of the series frequently exhibit higher oxidation states. This helps determine the oxidation state of any one element in a given molecule or ion, assuming that we know the common oxidation states of all of the other elements. (iii) It is so because manganese (Mn) has five unpaired electrons and 2 electrons in s orbital which can take part in bond formation. (iii) It is due to weak metallic bonds due to completely filled d-orbitals. (a) (i) Refer Ans. to Q.29 (ii). (b) Explain the following: (ii) Oxalic acid (C2H204) Question 68: Describe the preparation of (ii) There occurs much more frequent metal-metal bonding in compounds of heavy transition elements (3rd series). (i) Refer Ans. Therefore all these three sub shells can participate. The oxidation state of a free element (uncombined element) is zero. The (n+l) values of the tree orbitals are as under: 5 f = 5 + 3 = 8. By that those ions become strong reducing or oxidizing agents respectively. The modern definition is more general. Question 3: (iii) Refer Ans. (ii) Why is actinoid contraction greater than lanthanoid contraction? (i) Many of the transition elements are known to form interstitial compounds, (ii) Cr is typically hard metal due to presence of large number of unpaired electrons, metal-metal interaction is strong whereas mercury does not have unpaired electrons and has large size, therefore, forms weak metallic bond. (ii) The lowest oxide of a transition metal is basic, the highest is amphoteric/ acidic. What is it due to and what consequences does it have on the chemistry of elements following lanthanoids in the periodic table? Answer: (a) Lanthanoids, mostly show +3 oxidation state but some of them show +2 and +4 oxidation states also due to the stability of electronic configuration (4f°, 4f7 and 4f14), e.g. Secondly, in transition elements, incoming electron goes to inner shell (d-orbitals), whereas in main group elements, the incoming electron goes to outermost shell. Answer: Question 37: to Q.16 (a) (ii). (a) Complete the following reactions in an aqueous medium: Answer: (ii) Zinc is not regarded as a transition element to Q.38 (i). (i) The transition metal ions are usually coloured in aqueous solutions. (i) Mn(II) ion shows maximum paramagnetic character amongst the bivalent ions of first transition series. Question 46: Why? The most common and stable oxidation state of Lanthanides is +3. (a) Refer Ans. to Q.41 (ii). Question 73: - 7927007 (b) (i) They show variable oxidation states. 1) Actinides show a wide range of oxidation states from + 3 to + 6. (i) Refer Ans. (ii) The E°M2+/M for copper is positive (0.34V). Answer: (i) Among lanthanoids, Ln(III) compounds are predominant. Question 23: 3MnO4– + 4H+ ———> Why does it show so? Transition elements show variable oxidation states because electrons from both s and d orbitals take part in bond formation. (i) It is because Cr2+ loses electron to become Cr3+ which is more stable due to half filled t2g orbitals, whereas Mn3+ will gain electrons to become Mn2+ which is more stable due to half filled d-orbitals. (ii) 5f orbitals have poor shielding effect than 4f orbitals, therefore, effective nuclear charge is more in actinoids than lanthanoids. Answer: Ytterbium (Yb) also shows +2 oxidation state. (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. (i) number of oxidation states exhibited (ii) formation of oxometal ions. Question 54: 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. (Atomic nos. (a) Complete and balance the following chemical equations: to Q.40 (iii). (iii) Actinoid elements show wide range of oxidation states. None of the oxygen-containing compounds are peroxides or superoxides. (iii) Most of the transition metal ions exhibit characteristic colours in aqueous solutions (ii) MnO- + 4H+ + 3e- ——-> Mn02 + 2H20 (i) Thf enthalpies of atomisation of the transition metals are high. (a) Describe the following characteristics of the first series of the transition metals and their trends in the series (Sc to Zn): Unusual oxidation state; Common only for the heaviest elements; No 2+ & Md 2+ are more stable than Eu 2+; Actinide An 2+ ions have similar properties to Lanthanide Ln 2+ and to Ba 2+ ions; rationalization of stabilities: Open University Course Book p. 54-56 +3. to Q.12 (a) (i). (iii) 2MnO4– + 16 H+ + 5C204– ———-> 2Mn+2 + 8H20 + 10CO2, Question 10: Examples of variable oxidation states in the transition metals. to Q.38 (ii). Answer: Question 21: The actinides (An) may be prepared by reduction of AnF3 or AnF4 with vapors of Li, Mg, Ca, or Ba at 1100-1400 C. (i) Transition metals and their compounds are generally found to be good catalysts. (a) (i) Oxygen can form double bond, therefore, it can form Mn207, whereas ‘F’ cannot form double bonds, so, it can form MnF4. (At. ... Why do actinoids show a wide range of oxidation states? (a) Why do transition elements show variable oxidation states? (iii) Refer Ans. Question 4: to Q.62 (a) (i). to Q.9 (ii). Existing Student Sign In x. Forgot password? Mn04– + 8H+ + 5e- ———–> to Q.5 (ii). (ii) CrO4– + H+ ——-> (i) The enthalpies of atomisation of transition metals are quite high. Completing the CAPTCHA proves you are a human and gives you temporary access to the web property. There are 15 known isotopes. Oxidation occurs when an atom, molecule, or ion loses one or more electrons in a chemical reaction. to Q.51 (i). Higher the oxidation state, more will be acidic nature, e.g. Question 55: (b) (i) Refer Ans. (iii) There is a greater range of oxidation states among the actinoids than among the lanthanoids. (a) Which metal in the first transition series (3d series) exhibits +1 oxidation state most frequently and why? Question 72: (iii) Lanthanum and Lutetium do not show colouration in solutions. Higher oxidation states are shown by chromium, manganese and cobalt. Explain the following observations: Answer the following: (a) What is the general electronic configuration of lanthanoids? (b) Why do actinoids show a wide range of oxidation states? (ii) There occurs much more frequent metal-metal bonding in compounds of heavy transition metals (i.e. (a) (i) Atomic and covalent radii: The atomic radii decrease’ from Sc to Cr because number of unpaired electrons increases, therefore, effective nuclear charge increases. Performance & security by Cloudflare, Please complete the security check to access. to Q.l. They also show +2, +3, and +4 oxidation states. (ii) It is due to small size, higher charge and presence of vacant d-orbitals of suitable energy. Another way to prevent getting this page in the future is to use Privacy Pass. (a) (i) Refer Ans. (ii) Metal-metal bonding is more frequent for the 4d and the 5d series of transition metals than that for the 3d series. Answer: (i) The enthalpies of atomization of transition elements are quite high. ⚛ a range of oxidation states ⚛ colours in their compounds ⚛ the ability to form a wide range of coordination compounds ⚛ paramagnetism (ability to attract a magnetic field) ⚛ less chemical reactivity than Group 1 (Alkali) metals and Group 2 (Alkali Earth) metals. to Q.9 (ii). Question 70: (ii) Cu(I) is not stable in an aqueous solution. Answer: (b) What is misch metal? The actinides successively fill the 5f sublevel. to Q. Why do actinoids show a wide range of oxidation states? However, occasionally in solutions or in solid compounds, +2 and +4 ions are also obtained. Describe the preparation of KMn04 from pyrolusite ore (MnO4). Give reasons : Some just lose one electron to form +3 … to Q.51 (ii) 2 MnO4 + 6H+ + 5NO2 – ———-> The actinoids show in general +3 oxidation state. (i) It is because 5f, 6d and 7s have comparable energy. When the manganese atom is oxidized, it becomes more electronegative. (i) It is because Cu2+ is more stable because hydration energy overcomes 2nd ionisation energy. The maximum oxidation state shown by the elements of first transition series increases from Sc to Mn and then decreases to Zn. Actinides show a variety of oxidation states from +3 to +6. to Q.60 (ii). - or - email: password: Log in Forgot password? (iii) The members of the actinoid series exhibit a larger number of oxidation states than the corresponding members of the lanthanoid series. (ii)Oxidation States. Consequences: (ii) It is due to presence of unpaired electrons which participate in metal-metal bonding in 5d series (3rd series). (i) Transition elements generally form coloured compounds. Taking another example from chromium chemistry involving only a change of oxidation state (from +2 to +3): Cloudflare Ray ID: 600a3b03883b16ee I know that this may be an overgeneralization, since depending on the type (i.e metals, non metals, etc) it will be different. (ii) Refer Ans. NCERT P Bahadur IIT-JEE Previous Year Narendra Awasthi MS Chauhan. (i) E° value for the Mn+3/Mn+2 couple is positive (+1.5 V) whereas that of Cr+3/Cr+2 is negative (-0.4 V). Addition of 3% misch metal to magnesium increases its strength and used in making jet engine parts. Similarity: Question 57: Write the ionic equations for the reactions involved. Answer: Answer: (iv) Name a member of the lanthanoid series which is well known to exhibit + 2 oxidation state. Some of them can be cut with a knife. 58)? (ii) Zr and Hf have almost identical radii. Examples of variable oxidation states in the transition metals. to Q.16 (a) (ii). (ii) Due to comparable energies of 5f, 6d and 7s orbitals. (i) ‘Mn’ shows maximum number of oxidation states; +2, +3, +4, +6, +7. Physics. All of the values comes out to be same . Account for the following: Please enable Cookies and reload the page. (ii) Lanthanoids show limited number of oxidation state, viz. (i) Why is E (Cu 2 + / Cu) 0 value exceptionally positive? Answer: Answer: Explain the following observations: to Q.29 (i). (iii) The metal-metal bonding is more frequently found with the second and third series of transition elements. Question 7: Answer: (a) A blackish brown solid ‘A’ when forced with alkali metal hydroxide in presence of air, produces a dark green coloured compound ‘B’, which on electrolytic oxidation in alkaline medium gives a dark purple coloured compound ‘C’. • (iii) Refer Ans. (b) (i) It is because of strong metallic bonds due to large number of unpaired electrons in d-orbitals. Actinides with oxidation state +6, except for the AnO 2 2+-type cations, form [AnO 4] 2−, [An 2 O 7] 2− and other complex anions. Manganese: Manganese has a very wide range of oxidation states in its compounds. Unusual oxidation state; Common only for the heaviest elements; No 2+ & Md 2+ are more stable than Eu 2+; Actinide An 2+ ions have similar properties to Lanthanide Ln 2+ and to Ba 2+ ions; rationalization of stabilities: Open University Course Book p. 54-56 +3. (i) Many of the transition elements and their compounds can act as good catalysis. (ii) Mn04- + 4H+ + 3e- ———> ‘ (i) Highest fluoride of Mn is MnF4 whereas the highest oxide is Mn2O2 (ii) There is a close similarity in physical and chemical properties of the 4d and 5d series of the transition elements, much more than expected on the basis of usual family relationship. (ii) Unlike Cr3+, Mn2+, Fe3+ and the subsequent other M2+ ions of the 3d series of elements, the 4d and the 5d series metals generally do not form stable cationic species. Explain the following observations: Please do not block ads on this website. The transition elements do have low ionization energies, however, so they exhibit a wide range of oxidation states. Hence, it shows maximum number of oxidation states. (i) Cu+ is unstable in an aqueous solution. (a) The decrease in atomic and ionic size with increase in atomic number is called lanthanoid contraction. (ii)Oxidation States. (i) It is because of strong metallic bonds due to large number of unpaired electrons in d-orbitals. This is because of large energy gap between 4f 5d and 6s subshell. For example: 8788563422. 12 (a) (i). What is meant by ‘lanthanoid contraction’? (b) (i) 2KMn04———> K2Mn04+ MnO2+ O2 (ii) Refer Ans. (a) (i) Refer Ans. to Q.47 (i) (a) Calculate the number of unpaired electrons in the following gaseous state ions: Manganese: Manganese has a very wide range of oxidation states in its compounds. Zn+2 salts are white while Cu+2 salts are coloured. (ii) Refer Ans. (ii) Why is E (Mn 2 + / Mn) 0 value highly negative as compared to other elements? (b) Misch metal is an alloy which contains some of the lanthanoid metals. 2) This is due to very small energy gap b/w 5 f , 6 d and 7 s subshells. (b) Complete the following equations: (i) MnO is basic whereas Mn207 is acidic in nature. (i) Name the element of 3d transition series which shows maximum number of oxidation states. (i) Metal-metal bonding is more extensive in the 4d and 5d series of transition elements than the 3d series. * Actinides show a variety of oxidation states from +3 to +6. (i) Name the element showing maximum number of oxidation states among the first series of transition metals from Sc (Z = 21) to Zn (Z = 30). (ii) Chromium is typical hard metal while mercury in liquid, explain. Question 32: Question 17: Answer: (ii) Refer Ans. Actinides are typical metals. (ii) Transition metals form coloured compounds (i) Mn because it has five unpaired electrons and 2 electrons in s-orbital which can take part in bond formation, therefore, it shows maximum number of oxidation states. Answer: (iii) Strong oxidising agents provide energy for loss of one more electron from Co2+. (ii) Strong ligand provides energy which overcomes third ionisation energy to form Co3+ ion which forms more stable complex than Co2+. ions have incompletely filled d-orbitals. to Q.30 (iii). (a) How would you account for the following: (a) Complete the following chemical reaction equations: (ii)Sc3+ does not have unpaired electrons, therefore, cannot undergo d-d transition by absorbing light from visible region. Find 1 Answer & Solution for the question Why do actinoids show a wide range of oxidation states ? (iii) Refer Ans. (ii) Mn(III) undergoes disproportionation reaction easily. The principal oxidation states are +3 and +4 and +3 oxidation state is the most stable. Actinoids also show stable +3 oxidation state but show a number of oxidation states i.e. to Q.67 (ii). (iii) It is due to low sublimation energy, low and ionisation enthalpy and high hydration energy. (ii) Transition metals form a large number of complexes. Obviously, reaction (4.4.17) right is the reverse of reaction (4.4.11).From laboratory investigations and studies of plant data, it has been noticed that reaction (4.4.17) does not reach the equilibrium. 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. Answer: MnO4– + 8H+ + 5e- ———-> (b) (i) Refer Ans. This is due to the very small energy gap between 5f, 6d and 7s sub shells. (ii) It is due to increase in effective nuclear charge gradually because unpaired electrons increase in the beginning and then decrease. Why? Lanthanides show variable oxidation states. View Answer. Answer: The most stable oxidation state for lanthanide atoms is +3, but the +2 and +4 oxidation states are also common. Answer: Question 74: because they are bigger, the outermost shell is further away from the nucleus. Nos. The actinoids (5f-element) exhibit more number of oxidation states in general than the lanthanoids because 5f orbitals extend farther from the nucleus than the 4f-orbitals. Question 44: : La = 57, Lu = 71) (b) Account for the following: (i) It is due to lanthanoid contraction which is due to poor shielding effect of f-electrons. Refer Ans. (ii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state. The energies are decided on the basis of (n+l) rule. Question 42: (iii) It is due to involvement of unpaired ((-electrons to form strong metallic bond. Question 47: (Comptt. Answer: It is because Cu+2. Create free account. Your IP: 37.17.224.90 The earliest actinides have a closer relation to the transition metals, where the oxidation state is equal to the number of electrons on the outer shell. to Q.16 (a) (ii). Question 38: (i) Refer Ans. (i) They show variable oxidation state. (a) Complete the following chemical equations for reactions: 5f, 6d and 7s levels having comparable energies. Lanthanoids show mostly +3 oxidation state. (iii) It is because oxygen and fluorine are strong oxidising agents, highly electronegative, small size and can provide energy for formation of transition metal ion in higher oxidation state. Iron: Iron has two common oxidation states (+2 and +3) in, for example, Fe 2 + and Fe 3 +. (ii) Transition metals form alloys. Stability of oxidation states. When present in most compounds, hydrogen has an oxidation state of +1 and oxygen an oxidation state of −2. Actinoids can lose electrons from 7s, 6d and 5/ orbitals easily due to comparable energies and show higher oxidation states +4 and +6. 12 (a) (i). Assign reasons for the following :
(i) Copper (I) ion is not known in aqueous solution. to Q.5 (ii). (iv) Mn3+ (3d4) has 4.unpaired electrons, therefore, it is more paramagnetic than Cr3+) which has three unpaired electrons. (a) Account for the following: (b) What is lanthanoid contraction? (ii) The metallic radii of the third (5d) series of transition metals are virtually the same as those of the corresponding group members of the second (4d) series. to Q.9 (i). (a) Write the electronic configuration of Ce3+ ion, and calculate the magnetic moment on the basis of ‘spin-only’ formula. Misch metal is used in Mg-based alloy to produce bullets, shell and lighter flint. (b) Complete the following equation: (ii) Ce shows +4 oxidation state. Question 40: (i) Refer Ans. The reason for greater range of oxidation states in actinoids is attributed to. It also has a less common +6 oxidation state in the ferrate(VI) ion, FeO 4 2-. (i) Refer Ans. See also: Why is WF6 stable whereas CrF6 is unknown? 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