(ii) 2Na2Cr04 + H2S04(conc.) Question 51: Cloudflare Ray ID: 600a3b03883b16ee How would you account for the following: Now, it is known that all of the lanthanides can form +2 complexes in solution. Write two characteristics of the transition elements. (ii) Mns+(3d4) is strongly oxidising, whereas Cr2+(3d4) is strongly reducing. Mn207. However, they are difficult to separate from one another. (b) Explain the following observations about the transition/inner transition elements: – Why Zn generally do not show oxidation state greater than 2 ? 9. (ii) They form coloured ions. Explain the following observations: (i) Potassium dichromate from sodium chromate and Atomic number (Z) = 27. (i) Mn04– + C2072- + H+ ——-> (i) Highest fluoride of Mn is MnF4 whereas the highest oxide is Mn2O2 (b) (i) Calculate the spin magnetic moment of M2+(aq) ion. Question 15. (ii) Refer Ans. (a) Mn2+ has 3d5 (stable electronic configuration), therefore, it does not get oxidised to Mn3+, whereas Fe2+ has 3d6 which readily changes to Fe3+ (3d5), which has stable electronic configuration. Account for the following: MnO. Many of the transition metals can lose two or three electrons, forming cations with charges of +1 or +2. Question 47: Taking another example from chromium chemistry involving only a change of oxidation state (from +2 to +3): (iii) There is a greater range of oxidation states among the actinoids than among the lanthanoids. Write on similarity between the chemistry of lanthanoids and actinoids. The word valence is used inconsistently to mean either one or the other. (i) MnO is basic whereas Mn207 is acidic in nature. (b) How would you account for the following: (ii) It is because Mn2+ is more stable than Mn3+ due to stable half filled 3d° configuration: Secondly, in transition elements, incoming electron goes to inner shell (d-orbitals), whereas in main group elements, the incoming electron goes to outermost shell. What is meant by ‘lanthanoid contraction’? (a) How would you account for the following: (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). (i) Refer Ans. because they are bigger, the outermost shell is further away from the nucleus. The most common oxidation state; The most stable oxidation state for all trans-Americium elements (except No? The actinoids exhibit more number of oxidation states in general than the lanthanoids. Answer: Question 8: Question 9: (iv) Mn3+ (3d4) has 4.unpaired electrons, therefore, it is more paramagnetic than Cr3+) which has three unpaired electrons. Chemistry. Answered By . to Q.30 (iii). to Q.23 (a). (iii) It is due to lanthanoid contraction. Misch metal is an important alloy which contains some of the lanthanoid metals. Thus, the attraction on the 5f electrons in the actinoid series decreases. (ii) Refer Ans. Answer: It also has a less common +6 oxidation state in the ferrate(VI) ion, FeO 4 2-. Copper is the only metal in the first series of transition elements showing this behaviour. (iii) It is because lanthanoid lose 2 electrons from 6s orbitals and one from 5d – or 4/ orbitals and are stable in +3 oxidation state. (b) What are the common oxidation states of Cerium (At.no. Oxidation occurs when an atom, molecule, or ion loses one or more electrons in a chemical reaction. Completing the CAPTCHA proves you are a human and gives you temporary access to the web property. Write the ionic equations for the reactions involved. Answer: (b) (i) Refer Ans. Why? (a) Which metal in the first transition series (3d series) exhibits +1 oxidation state most frequently and why? (ii) E°CU2+/CU *ias +ve value due to high ionisation enthalpies and sublimation energies and lower hydration energy. (iii) Cobalt (II) is stable in aqueous solution but in the presence of complexing agents, it is easily oxidised. The actinoids show in general +3 oxidation state. (b) (i) Refer Ans. Electrons do not flow around by themselves but they must be provided by some sources . Question 46: Assign reasons for the following: Manganese: Manganese has a very wide range of oxidation states in its compounds. Iron: Iron has two common oxidation states (+2 and +3) in, for example, Fe 2 + and Fe 3 +. (iii) Refer Ans. * The principal oxidation states are +3 and +4 and +3 oxidation state is the most stable. (b) What is misch metal? to Q.38 (ii). Answer: (i) It is because Cu2+ is more stable because hydration energy overcomes 2nd ionisation energy. View Answer. The most important isotope is 239 Pu because it is fissionable and has a half-life of 24,100 years, which makes it easy for chemists to study. (i) It is due to presence of five unpaired electrons. On the other hand Actinoids show a large number of oxidation states because of small energy gap between 5f, 6d and 7s subshell. (ii) Refer Ans. (ii) The enthalpy of atomization is lowest for Zn in 3 d series of the transition elements. (iii) Among the 3d series of transition elements, the largest number of oxidation states are exhibited by manganese. Answer: Question 21: Answer: (i) Cu+ is unstable in an aqueous solution. (At. (ii) The actinoids exhibit a large number of oxidation states than the corresponding members in the lanthanoid series. (ii) Actinoids exhibit greater range of oxidation states than lanthanoids. It exhibits O.S. (iii) MnO- + 8H4 + 5e- ———> Mn2+ + 4H20 (At. Sc3+, V3+, Ti4+, Mn2+ (b) (i) Refer Ans. Why does it show so? Examples of variable oxidation states in the transition metals. (iii) Most of the transition metal ions exhibit characteristic colours in aqueous solutions (iii) Actinoids show a wide range of oxidation states. Question 4: (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. Identify A, B, C and write the reactions involved. to Q.43 (b) (ii) to Q. to Q.38 (i). You may need to download version 2.0 now from the Chrome Web Store. (ii) Chromium is typical hard metal while mercury in liquid, explain. (i) It is due to lanthanoid contraction which is due to poor shielding effect of f-electrons. (c) Which of the 3d-block elements may not be regarded as the transition elements and why? The actinoids exhibit more number of oxidation states in general than the lanthanoids. 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. 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. (ii) It is because energy required to remove electron is more due to greater effective nuclear charge which is due to lanthanoid contraction. (ii) The lowest oxide of a transition metal is basic, the highest is amphoteric/ acidic. (a) Copper exhibits +1 oxidation state frequently due to stable electronic configuration. The radioactive nature of actinoids. (iii) Ionisation enthalpies: There is slight and irregular variation in ionisation energies of transition metals due to irregular variation of atomic size. They also show +2, +3, and +4 oxidation states. Answer the following: (a) What is the general electronic configuration of lanthanoids? (ii) MnO- + 4H+ + 3e- ——-> Mn02 + 2H20 Elements in other states hence try to lose or gain electrons to get +3 state. to Q. 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. The modern definition is more general. Account for the following: (a) Describe the following characteristics of the first series of the transition metals and their trends in the series (Sc to Zn): Why Lanthanide show Variable Oxidation State? (iii) Actinoid elements show wide range of oxidation states. Actinoids can lose electrons from 7s, 6d and 5/ orbitals easily due to comparable energies and show higher oxidation states +4 and +6. Oxidation State of Actinides. (i) Refer Ans. Sc shows maximum + 3 and Mn shows + 7, V( + 5), Gr( + 6), Fe( + 3), Ni( + 2), Co( + 3), Cu( + 2) and Zn( + 2) oxidation state. (ii) It is due to 5f electrons which are more effectively shielded than 4f electrons therefore, outer electrons are less firmly held and available for bonding in actinoids and they show a wide range of oxidation states. Read the numbers at the top of the columns. (ii) Cr2O7-(aq) + H2S(g) + H+(ag) ——–> I’ve noticed that some answers refer to the word valence as if you mean number of bonds and other answers refer to the word as if it means the charge. It is due to similar energy of (n – 1 )d and ns orbitals, electrons from both can be lost. (ii) It is due to large number of unpaired electrons in the middle of series of transition metals. But the most common oxidation state of actinoids is +3. to Q.16 (a) (i). Question 64: (ii) Ce shows +4 oxidation state. Lanthanoids show mostly +3 oxidation state. Question 42: to Q.40 (iii). Explain the following observations: How would you account for the following? It produces dark green K2Mn04 which undergoes oxidation as well as reduction in neutral or acidic solution to give permanganate. (c) Sc3+ is colourless in aqueous solution, whereas Ti3+ is coloured. Answer: Answer: (Comptt. (i) It is because 5f, 6d and 7s have comparable energy. Determine the oxidation states of the elements in the compounds listed. Therefore, its salts are white. Answer: (i) It is due to presence of vacant d-orbitals of suitable energy, smaller size of cations and higher charge. (iii) Refer Ans. (iii) There is hardly any increase in atomic size with increasing atomic numbers in a series of transition metals. (b) (i) Refer Ans. (iii) Strong oxidising agents provide energy for loss of one more electron from Co2+. to Q.23 (b). Question 71: (ii) It is due to increase in effective nuclear charge gradually because unpaired electrons increase in the beginning and then decrease. 1A = 1 valance electron of the alkali metals. Why dp transition elements show variable oxidation states? (ii) It is due to large number of unpaired electrons in d-orbitals in middle of the series. (b) What are the common oxidation states of Cerium (At.no. Another way to prevent getting this page in the future is to use Privacy Pass. How would you account for the following? (ii) Refer Ans. Why? what are the most common oxidation states of iron. (ii) Refer Ans. (ii) Due to comparable energies of 5f, 6d and 7s orbitals. To reach a higher oxidation state, one obviously has to pay for it in the form of ionisation energy/energies. * Actinides show a variety of oxidation states from +3 to +6. Question 43: to Q.9 (i). (iii) Lanthanum and Lutetium do not show colouration in solutions. to Q.30 (iii) Example: TPSS 435 It is because neither Zn nor Zn+2. What happens when an acid solution of green coloured compound (B) is allowed to stand for some time. (ii) There occurs much more frequent metal-metal bonding in compounds of heavy transition metals (i.e. How would you account for the following: (i) Why do actinoids show wide range of oxidation states? Assign reasons for the following: Answer: to 0.5 (i). (iii) Complete the following equation: Mention its two uses. . (iii) The highest oxidation state of a transition metal is exhibited in its oxide or fluoride. (ii) Na2Cr207 from Na2Cr04? (i) Small size atoms, such as B, C and H can occupy voids present in transition metals. (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. Answer: Though 3+ is the most stable oxidation state, other oxidation states are possible because of the good shielding of f-electrons. 16 (a) (ii). (a) (i) 2Mn02 + 4KOH + 02——–> 2K2Mn04 + 2H20 that means the ionization energy is lower for the corresponding oxidation state compared to lanthanides. (i) In the series Sc (Z = 21) to Zn (Z = 30), the enthalpy of atomisation of Zn is the lowest. (i) It is due to smaller size of transition metals and strong metallic bonds due to presence of large number of unpaired electrons. How does the acidified permanganate solution react with the following: 5 (ii). 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. Question 37: In addition, actinides show oxidation states such as +4, +5 and +6. Write one similarity between the chemistry of lanthanoids and actinoids. Although the lanthanides are sometimes called the rare earths, the elements are not particularly rare. (a) (i) Transition elements form interstitial compounds. to Q.30 (i). The principal oxidation states are +3 and +4 and +3 oxidation state is the most stable. (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. (ii) It is due to poor shielding effect of 4f orbitals, more unpaired electrons take part in metallic bond formation. (iii) Transition metals and their compounds act as catalyst. (ii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state. (b) It contains 95% lanthanoid metal, 5% iron and traces of S, C, Ca and AI. (iii) Transition metals in general act as good catalysts. Write one similarity and one difference between the chemistry of lanthanoids and that of actinoids. (iv) It is because of high ionisation enthalpy of Cu which is not compensated by hydration energy. (iii) The metal-metal bonding is more frequently found with the second and third series of transition elements. Answer: (b) Complete the following equation: State reasons for the following observations: Common Oxidation States is +3 Th(+4),Pa(+5), U (+6) ,Np(+7) 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. Existing Student Sign In x. Forgot password? Answer: What is it due to and what consequences does it have on the chemistry of elements following lanthanoids in the periodic table? (b) (i) 2KMn04———> K2Mn04+ MnO2+ O2 Ionic radii of bivalent cations decrease from Sc to Cu due to increase in number of protons. to Q.30 (i). Why? Addition of 3% misch metal to magnesium increases its strength and used in making jet engine parts. Answer: Few show +2 and +4, whereas Actinoids show +3, +4, +5, +6 and +7 oxidation states. Answer: f°,f7,f14. There is repulsion between paired electrons. (ii) Cr2O7-(aq) + Fe2+ (aq) + H+(aq) ——-> to Q.5 (ii). In 3d series (Sc to Zn), which element shows the maximum number of oxidation states and why? 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. For example: (i) It is due to weak metallic bond due to absence of unpaired electrons. Assign suitable reasons for the following: Answer: (i) The transition metal ions are usually coloured in aqueous solutions. (ii) It is due to increase in atomic mass and decrease in atomic size, therefore, density increases from Ti(22) to Cu(29). (b) Account for the following: Some just lose one electron to form +3 … (a) (i) Refer Ans. (ii) Strong ligand provides energy which overcomes third ionisation energy to form Co3+ ion which forms more stable complex than Co2+. (i) Cu+ ion is unstable in aqueous solutions. (iii) With the same d-orbital configuration (d4), Cr2+ ion is a reducing agent but Mn3+ ion is an oxidising agent. Stability of oxidation states. Actinides show variable oxidation states because of the smaller energy gap between 5f, 6 d and 7s orbitals. (iii) Refer Ans. Actinides show a variety of oxidation states from +3 to +6. 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. (iii) The members of the actinoid series exhibit a larger number of oxidation states than the corresponding members of the lanthanoid series. (i) Refer Ans. to Q.62 (a) (i). Lanthanoids show limited oxidation states(+2,+3,+4). (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. (i) Cr2+ is reducing in nature while with the same d-orbital configuration (d4) Mn3+ is an oxidising agent. Books. to Q.29 (i). (iii) Transition metals have high melting points. (ii) Why is actinoid contraction greater than lanthanoid contraction? The prominent oxidation state among actinides is +3. (a) (i) Refer Ans. to Q.47 (ii). (iv) The silver atom has completely filled d-orbitals (4d 10 ) in its ground state, yet it is regarded as a transition element. (a) (i) Cr2072- + 20H- ——–> 2CrO4– + H2O The most common oxides are of the form M 2 O 3, where M would be one of the elements in the Actinide series. • Answer: (i) It is because 5f, 6d and 7s have comparable energy. (iii) 2MnO4+ 4KOH + 02 ———> 2K2Mn04+ 2H20, Question 11: NCERT DC Pandey Sunil Batra HC Verma Pradeep Errorless. (i) Cr2072- + 20H- ———-> (i) Cu (I) ion is not stable in an aqueous solution. : La = 57, Lu = 71) (b) What is lanthanoid contraction? (iii) The members in the actinoid series exhibit a larger number of oxidation states than the corresponding members in the lanthanoid series. (ii) Manganese exhibits the highest oxidation state of+7 among the 3d series of transition elements (ii)Sc3+ does not have unpaired electrons, therefore, cannot undergo d-d transition by absorbing light from visible region. 3MnO4– + 4H+ ———> to Q.35 (i). (a) Refer Ans. (ii) Transition elements and their compounds are generally found to be good catalysts in chemical reactions. For example, in a sulfite ion (SO 3 2- ), the total charge of the ion is 2-, and each oxygen is assumed to be in its usual oxidation state of -2. 8. Actinides exhibits larger oxidation states than lanthanide because of very small energy gap between 5f, 6d and 7s subshells . This is because Option 1) the orbitals extend further from the nucleus than the orbitals Option 2) the orbitals are more buried than the orbitals Option 3) there is a similarity between and orbitals in their angular part of the wave function Option 4) the actinoids are more reactive than the lanthanoids. Question 5: Answer: (a) Write the electronic configuration of Ce3+ ion, and calculate the magnetic moment on the basis of ‘spin-only’ formula. Question 38: Answer: So, which do you mean? (i) Atomic radii (ii) Oxidation states (iii) Ionisation enthalpies Originally, the term was used when oxygen caused electron loss in a reaction. (b) (i) They show variable oxidation states. (ii) They form coloured compounds. Examples of variable oxidation states in the transition metals. Answer: Explain the following observations: Unlike Cr3+, Mn2+, Fe3+ & subsequent other M2+ ions of the 3d series of the elements , the 4d and 5d series metals generally do not form stable cationic species. Oxidation doesn't necessarily involve oxygen! +4, +5 and + 6, +7 due to small energy difference between 5f, 6d and 7s subshells. Answer: to Q.51 (i). Manganese: Manganese has a very wide range of oxidation states in its compounds. Answer: (a) (i) Refer Ans. Explain giving a suitable reason for each of the following: The transition elements do have low ionization energies, however, so they exhibit a wide range of oxidation states. Answer: In soils, the main source of electrons is carbon atoms of organic matter because carbon has a wide range of oxidation states. Answer: When oxidation occurs, the oxidation state of the chemical species increases. Describe the preparation of • 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. Answer: Write its one use. Answer: ⚛ 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. (iii) It is due to weak metallic bonds due to completely filled d-orbitals. 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