Compare the chemistry of the actinoids with that of lanthanoids with reference to (i) electronic configuration (ii) oxidation states and (iii) chemical reactivity. This half-full set of 'd' orbitals is spherically symmetrical and has an extra degree of stability. Alloys are homogeneous solid solutions in which the atoms of one metal are distributed randomly among the atoms of other. It forms compounds like CuCl 2 and also with oxygen like CuO. Question 12. (ii) Because of large number of unpaired electrons in their atoms they have stronger interatomic interactions and hence stronger metallic bonding between atoms resulting in higher enthalpies of atomisation. This contraction is attributed to the imperfect shielding of one electron by another in the same sub-shell. (ii) Oxidations states : Elements show variable oxidation states in both the series. Solution: scandium (n-1) stands for penultimate shell and d-orbitals may have one to ten d electrons and n denotes valence s or the outermost shell which can have one or two electrons. Which of the 3d series of the transition metals exhibits the largest number of oxidation states and why? Explain briefly how +2 state becomes more and more stable in the first half of the first row With increasing atomic number the transition elements with increasing atomic numbers? i) Except scandium, the most common oxidation state of the first row transition elements is +2 which arises from the loss of two 4s electrons, which means that These values correspond to the numbers of valence shell electrons in the atoms of these elements. Use Hund’s rule to derive the electronic configuration of Ce3+ ion, and calculate its magnetic moment on the basis of ‘spin-only’ formula. See also: oxidation states in {{infobox element}} The oxidation states are also maintained in articles of the elements (of course), and systematically in the table {{Infobox element/symbol-to-oxidation-state}} (An overview is here). (iv) atomic sizes. Solution: Both 3d and 4s electrons can participate in bonding. The energy separation (gap) of splited energy level is called 10 Dq. (iii) The highest oxidation state is exhibited in oxoanions of a metal. Solution: They have high melting points, higher than those of pure metals. Choose the best answer: 1. Free elements (elements that are not combined with other elements) have an oxidation state of zero, e.g., the oxidation state of Cr (chromium) is 0. (ii) Manganese exhibits the highest oxidation state of+7 among the 3d series of transition elements Answer: (i) Refer Ans. Oxidation number of element in a compound can be positive or negative or may be zero. Actinoids show the oxidation state from +3 (most common) to +7, while lanthanoids show the oxidation state from +3 up to + 7. There is no d 4 configuration in ground state, as it becomes 3d 5 4s 1 Question 6. Misch metal is an alloy which contains some of the lanthanoid metals. Students who are preparing for their Class 12 exams must go through NCERT Solutions for Class 12 Chemistry Chapter 8 The d and f Block Elements. Try to correlate this type of behaviour with the electronic configurations of these elements. Give reasons for each. state & by the loss of one more electron from the 3d-orbital, it acquires. Permanganate ion, MnO4– contains Mn in its highest oxidation state of +7. common) oxidation state”. The potassium manganate is extracted by water, which then undergoes disproportionation in neutral or acidic solution to give potassium permanganate. Because of small size and high electronegativity oxygen or fluorine can oxidise the metal to its highest oxidation state. On the other hand, Mn shows the highest oxidation state of +4 with fluorine because it can form a single bond only. A single unpaired electron has a magnetic moment of 1.73 Bohr magneton (BM). But some types of atoms such as chlorine form various oxidation numbers like -1, 0, +1, +3, +5, +7 oxidation numbers in compounds. Remember: Oxidation involves an increase in oxidation state. When iso–propyl iodide is boiled with aqueous potassium hydroxide then iso–propyl alcohol is formed. These facts render their study more difficult. Compare the general characteristics of the first series of transition metals with those of the second and third series metals in the respective vertical columns. This oxidation state arises from the loss of two 4s electrons. Paramagnetism – The ions with unpaired electrons are paramagnetic. show only +2 and +3 oxidation states, Due Question 2. +2 and +4 oxidation states are exhibited due to extra stability of empty, half – filled or fully filled f – subshells. (i) electronic configuration One of the most striking features of the transition elements is that the elements usually exist in several different oxidation states. Describe trend in the standard electrode potential values of the transition series and chemical reactivity. 2CrO42- + 2H+ → Cr2O72- + H2O The elements which show largest number of oxidation states occur in or near the middle of series (i.e., 4s 2 3d 3 to 4s 2 3d 7 configuration). Clearly, the +2 oxidation state arises from the loss of the 4s electrons. 3d 4 : Stable oxidation state will be +3 and +6 due to outer electronic configuration 3d 4 4s 1. In case of Fe2+ ion, the third electron is taken out from 3d6 configuration which results in more stable 3d5 configuration. Solution: (i) Of the d4 species, Cr2+ is strongly reducing while manganese(lll) is strongly oxidising. Solution: Solution: The common oxidation state of 3d series elements is + 2 which arises due to participation of only 4s electrons. Match the statements given in Column I with the oxidation states given in Column II. Scandium is one of the two elements in the first transition metal period which has only one oxidation state (zinc is the other, with an oxidation state of +2). Write down the number of 3d electrons in each of the following ions: Ti2+, V2+, Cr3+, Mn2+, Fe2+, Fe3+, CO2+, Ni2+ and Cu2+. (iii) d1 configuration is very unstable in ions because after losing one more electron it will become more stable due to vacant d-orbital. What are the different oxidation states exhibited by the lanthanoids? The 5f electrons are more effectively shielded from nuclear charge. Sulfur. Explain why Cu+ ion is not stable in aqueous solutions? Question 31. The common oxidation states are +2 and +3. Solution: Question 10. Fresh iron surfaces appear lustrous silvery-gray but oxidize in normal air to give iron oxides, also known as rust. To what extent do the electronic configurations decide the stability of oxidation states in the first series of the transition elements? The colour observed corresponds to the complementary colour of the light absorbed. Among the elements of 4d-Series Ruthenium belonging to 8th group exhibits maximum oxidation state. Sodium dichromate is more soluble than potassium dichromate. The stability of oxidation state depends mainly on electronic configuration and also on the nature of other combining atom. (ii) Co(II) gets oxidised to Co(III) in presence of complexing agent because Co(III) is more stable than Co(II). Na2Cr2O7 + 2KCl → K2Cr2O7 + 2NaCl CH ₃ I > CH ₃ Br > CH ₃ Cl > CH₃F 4) As branching in alkyl halide increases the boiling point of alkyl halide decreases. Answer. Electrolytically : Question 17. Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements. H 2 O,  NH 3 ). Decrease in size between two successive elements is higher in actinoids due to poor screening by 5f electrons. Give two examples of disproportionation reaction in aqueous solution. 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Maintenance & improvements. Oxidation state of 4d series. While for the alkaline earth elements of group II, they are 2. Answer. Question 10. iii) Metal ion & ligands are considered point charges. When the ethylenediaminetetraacetate ion (EDTA4-) forms a complex with a transition metal ion, how many electrons does it normally donate to the metal? The element has the configuration [Ar]4s 2 3d 6. Metallic character – With the exceptions of Zn, Cd and Hg, they have typical metallic structures. Question 26. Solution: (iii) Ionisation enthalpies : The ionisation enthalpies in each series generally increases gradually from left to right. After removing the ns-electron, the remainder is called core. CBSE Maths notes, CBSE physics notes, CBSE chemistry notes. Titanium, Chromium, and Manganese. The chemistry of the actinoid elements is not so smooth as that of the lanthanoids. Name the members of the lanthanoid series which exhibit +4 oxidation state and those which exhibit +2 oxidation state. (ii) atomic and ionic sizes These do not correspond to any normal oxidation state of the metal. Solution: The tendency to show highest oxidation state increases from Sc to Mn, then decreases due to pairing of electrons in 3d subshell. Question 8. The latter members could be prepared only in nanogram quantities. Oxidation number of (group I) elements like … Justify this statement by giving some examples from the oxidation state of these elements. Students can also download NCERT Solutions for Class 12 Chemistry Chapter 8 The d and f Block Elements PDF to access them even in offline mode. Solution: Molybdenum exhibits oxidation states of +2 to +6 and is considered to display the zero oxidation state in the carbonyl Mo(CO) 6. Lanthanoids liberate hydrogen from dilute acids and burn in halogens to form halides. Solution: Question 25. Solution: However, the shielding of one 4f electron by another is less than one d electron by another with the increase in nuclear charge along the series. Question 5. For ions, the oxidation state is equal to the charge of the ion, e.g., the ion Fe 3 + (ferric ion) has an oxidation state of +3. 2Cu+(aq) → Cu2+(aq) + Cu(s) Except scandium, the most common oxidation state shown by the elements of first transition series is +2. 5) Alkyl halides are readily soluble in organic solvent but slightly soluble in water. 7 electrons which is maximum in 3d series. In the formation of a transition metal complex, the central metal atom or ion acts as . Try to correlate this type of behaviour with the electronic configurations of these elements. Because the distribution of oxidation states among the actinoids is so uneven and so different for the earlier and latter elements. The actinoids show in general +3 oxidation state. Furthermore, the oxidation states change in units of one, e.g. Compounds having oxidation states +2 and +3 of these elements have ionic bonds whereas bonds are essentially covalent in higher oxidation states. 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