8.11 Write down the electronic configuration of: (i) Cr3+ (iii) Cu+ (v) Co2+ (vii) Mn2+ (ii) Pm3+ (iv) Ce4+ (vi) Lu2+ (viii) Th4+ 

<p><strong>8.11&nbsp; (i)</strong> The atomic number of Cr is 24 and the electronic configuration is [Ar] 3d⁵4s^1.When 3 electrons are removed, it becomes Cr³⁺. The electronic configuration of Cr³⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d³ Or [Ar]3d³</p><p>&nbsp;</p><p><strong> (ii)</strong> The atomic number of Pm is 61 and the electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁵ 5s² 5p⁶ 6s² or [Xe] 4f⁵6s². When 3 electrons are removed, it becomes Pm⁺³, having the electronic configuration, </p><p>Pm³⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f⁴</p><p>Or, [Xe]⁵⁴4f⁴</p><p>&nbsp;</p><p><strong> (iii)</strong> The atomic number of Cu is 29 and has the electronic configuration of [Ar] 3d¹⁰4s¹. On removing one electron, the Cu⁺is obtained with the electronic configuration, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ Or [Ar] 3d¹⁰</p><p>&nbsp;</p><p><strong> (iv)</strong> The atomic number of Ce is 58 and has the electronic configuration of [Xe] 4f¹5d¹6s². When the valence electrons are removed, the Ce⁴⁺ ion with configuration, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ Or [Xe] is obtained.</p><p>&nbsp;</p><p><strong> (v)</strong> The atomic number of Co is 27 and has the electronic configuration of [Ar] 3d⁷4s². When 2 electrons are removed from s-orbital, it becomes Co²⁺with electronic configuration, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷ Or, [Ar] 3d⁷.</p><p>&nbsp;</p><p><strong> (vi)</strong> The atomic number of Lu is 71 and has the electronic configuration of [Xe] 4f¹⁴5d¹6s². When 2 electrons are removed, Lu²⁺with the configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f ¹⁴ 5d ¹ Or, [Xe] 4f¹⁴5d¹</p><p>&nbsp;</p><p><strong> (vii)</strong> The atomic number of Mn is 25 and has the electronic configuration of [Ar] 3d⁵4s² . When 2 electrons are removed, Mn²⁺ ion is obtained and has an electronic configuration of 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ Or, [Ar]¹⁸ 3d¹⁰ .</p><p>&nbsp;</p><p><strong> (viii)</strong> The atomic number of Th is 90 and has the electronic configuration of [Rn] 6d² 7s² . When 4 electrons are removed, the electronic configuration becomesTh⁴⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f ¹⁴ 5d ¹⁰ 6s ² 6p ⁶ Or, [Rn]</p>

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