Write one similarity between the chemistry of lanthanoids and actinoids. because they are bigger, the outermost shell is further away from the nucleus. (a) Refer Ans. (i) Transition metals show variable oxidation, states. (iv) Name a member of the lanthanoid series which is well known to exhibit + 2 oxidation state. (ii) Chromium is typical hard metal while mercury in liquid, explain. (iii) The metallic radii of the third (5d) series of transition metals are nearly the same as those of the corresponding members of the second series. Answer: (ii) It is due to large number of unpaired electrons in d-orbitals in middle of the series. (a) Complete the following chemical equations for reactions: (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) Metal-metal bonding is more frequent for the 4d and the 5d series of transition metals than that for the 3d series. Answer the following: (a) What is the general electronic configuration of lanthanoids? Explain the following: 58)? The E 0 ( M 2+ / M ) value of a metal depends on the energy changes involved in the formation of the M 2+ ion: (iii) Which is a stronger reducing agent Cr 2 + or Fe 2 +? (iv) The silver atom has completely filled d-orbitals (4d 10 ) in its ground state, yet it is regarded as a transition element. Now, it is known that all of the lanthanides can form +2 complexes in solution. : La = 57, Lu = 71) C. 5f, 6d and 7s levels having comparable energies. (b) What is lanthanoid contraction? (iv) It is because of high ionisation enthalpy of Cu which is not compensated by hydration energy. Answer: (a) How would you account for the following: (i) It is because they show variable oxidation states and have vacant rf-orbitals Write on the similarity between the chemistry of lanthanoids and actinoids. Dissimilarity: (Atomic nos. 8. (i) Thf enthalpies of atomisation of the transition metals are high. You are very important to us. Answer: (ii) It is due to lanthanoid contraction, the ionic size of 4d and 5d transition series in similar. Assign reasons for the following :
(i) Copper (I) ion is not known in aqueous solution. Actinides exhibits larger oxidation states than lanthanide because of very small energy gap between 5f, 6d and 7s subshells . (ii) Tendency to form oxometal ions increases from Sc to Cr and then decreases due to increase in unpaired electrons and ability to form multiple bonds with oxygen. 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. Actinoid contraction is greater from element to element than lanthanoid contraction. Account for the following: It is attained by removing outermost 2 electrons of 6s electrons and 1 electron from 4f electrons. (i) Small size atoms, such as B, C and H can occupy voids present in transition metals. On the other hand Actinoids show a large number of oxidation states because of small energy gap between 5f, 6d and 7s subshell. to Q.38 (ii). (i) The gradual decrease in size (actinoid contraction) from element to element is greater among the actinoids than that among the lanthanoids (lanthanoid contraction). to Q.16 (a) (ii). (b) Why do actinoids show a wide range of oxidation states? (a) (i) Refer Ans. (ii) Among the divalent cations in the first series of transition elements, manganese exhibits the maximum paramagnetism. (ii) It is due to similarity in atomic and ionic size, there is more horizontal similarity. Answer: Oxidation doesn't necessarily involve oxygen! Question 29: (iii) It is because 5f, 6d and 7s have comparable energy. To reach a higher oxidation state, one obviously has to pay for it in the form of ionisation energy/energies. The highest oxidation state is equal to the total number of electrons in s as well as of-orbitals. The actinides successively fill the 5f sublevel. (i) It is due to presence of vacant d-orbitals of suitable energy, smaller size of cations and higher charge. (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. On the other hand Actinoids show a large number of oxidation states because of small energy gap between 5f, 6d and 7s subshell. Question 69: (ii) Ce shows +4 oxidation state. Question 26: Example: TPSS 435 The maximum oxidation state shown by the elements of first transition series increases from Sc to Mn and then decreases to Zn. Answer: Question 2: Question 24: 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. (At. to Q.30 (i). It contains 45% lanthanoid metals and iron (5%) and traces of S, C, Ca and Al. (ii) The E value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+ couple or Fe3+/Fe2+ couple. (ii) Refer Ans. Question 53: (iii) Refer Ans. 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