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Justify the given statement with suitable examples- "the Properties of the elements are a periodic function of their atomic numbers". |
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Answer» Solution : There are so MANY physical properties of elements such as melting points, boiling points, heats of fusion and vaporisation, ENERGY of atomisation, etc., which show periodic variations. The cause of periodicity in properties is the repetition of same OUTER configurations after certain regular intervals. e.g., `1^(st)` group elements have almost same outer electronic configuration, i.e, `ns^(1)` `""_(3)Li=1s^(2),2s^(1)` `""_(11)Na=1s^(2),2s^(2),2p^(2),3s^(1)` `""_(19)K=1s^(2),2s^(2),2p^(6),3s^(2),3p^(6),3s^(1)` `""_(37)Rb=1s^(2),2s^(2),2p^(6),3s^(2),3p^(6),3d^(10),4s^(2),4P^(6),5s^(-1)` Due to same configuration all alkali metals have similar properties. e.g., SODIUM and potassium are soft and reactive metals. They forms basic oxides and their basic character increases as we go from top to bottom. They form +ve ion while lossing of one electron. All the elements of `17^(th)` group (halogen family) have same outermost shell electronic configuration, i.e., `ns^(2)np^(5)` and thus have similar properties. `""_(9)F=1s^(2),2s^(2),2p^(5)` `""_(17)Cl=1s^(2),2s^(2),2p^(6),3s^(2),3p^(5)` `""_(35)Br=1s^(2),2s^(2),2p^(6),3s^(2),3p^(6),3d^(10),4s^(2),4p^(5)` `""_(53)I=Is^(2),2s^(2),3s^(2),3d^(10),4s^(2),4p^(6),4d^(10),5s^(2),4p^(5)` `""_(85)At= 1s^(2),2s^(2),2p^(6),3s^(2),3p^(10),4s^(2),4p^(6),4d^(10),4f^(14),5s^(2),5p^(6),5d^(10),6s^(2),6p^(5)` |
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