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NCERT Class XII Chemistry
Chapter - The d- and f-Block Elements
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Question : 28 of 49
Marks: +1, -0
What are inner transition elements? Decide which of the following atomic numbers are the atomic numbers of the inner transition element :
29, 59, 74, 95, 102, 104.
Solution:  
Lanthanoids and actinoids are called inner transition elementsbecause inner f-orbitals are progressively filled and the last electron goesto anti-penultimate f orbital.
Elements with atomic number 59, 95, 102 are inner transition metalsbecause theybelong to lanthanoids and actinoids.
Pr(59) 1s22s22p63s23p64s23d104p65s24d105p66s24f3\mathrm{Pr}(59)\,1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{6}6s^{2}4f^{3}
Am(95) 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s25f7\mathrm{Am}(95)\,1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{6}6s^{2}4f^{14}5d^{10}6p^{6}7s^{2}5f^{7}
No(102) 1s22s22p63s23p63d104s24p64d104f145s25p65d105f146s26p67s2\mathrm{No}(102)\,1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{6}4d^{10}4f^{14}5s^{2}5p^{6}5d^{10}5f^{14}6s^{2}6p^{6}7s^{2}
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