Page 19 - Chemistry ICSE Class X
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Periodic Properties and Variations of Properties (Physical and Chemical)                              7
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          QH VJKU ITQWR  K G   lead (Pb) is a typical metal


          How does the metallic character vary in a period
          The metallic character decreases in going from left to right in a period.
              Therefore, the elements on the left side of the periodic table are metals,
          and those on the right are nonmetals                                                    Lead

          Period 3            Na      Mg      Al      Si      P       S      Cl
          Atomic number        11     12      13      14      15      16     17
                    Metallic character decreases in a period from left to right
              Explanation: As we go from left to right in a period, the nuclear charge
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          GNGEVTQPU CPF VJG VGPFGPE[ VQ NQUG GNGEVTQPU FGETGCUGU
              Therefore, the metallic character decreases across a period from left to
          TKIJV


          Nonmetallic Character

          The elements that show a tendency to  gain  one  or more electrons and
          form negative ions (anions) are called  nonmetals   6JWU   PQPOGVCNU  CTG
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                                             –
                         Cl(g)       +      e       o         Cl –
                          (2,8,7)                              (2,8,8)
                       chlorine atom                        chloride ion
                                             –
                                                               2–
                          O(g)       +     2e       o        O (g)
                          (2,6)                                (2,8)
                       oxygen atom                           oxide ion
              Nonmetals are placed on the right hand side, and in the upper middle
          RCTV QH VJG RGTKQFKE VCDNG

          On what factors does the nonmetallic character of an
          element depend
          Nonmetallic character depends upon the following two factors:
            ƒ  Atomic size. Smaller is the atom, greater is the nuclear pull on the
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               CEEGRV GNGEVTQPU KP KVU QWVGTOQUV UJGNN  6JGTGHQTG  VJG GNGOGPV JCXKPI
               smaller atom will be more nonmetallic
            ƒ  Nuclear charge. The greater is the nuclear charge, greater is the
               VGPFGPE[  VQ  CEEGRV ICKP  GNGEVTQPU   6JGTGHQTG   VJG  GNGOGPV  JCXKPI
               atom with greater nuclear charge will be more nonmetallic

          How does nonmetallic character vary in a group

          Nonmetallic character of elements in a group decreases as we go down
          the group  6JWU  KP CP[ ITQWR QH PQPOGVCNU VJG GNGOGPV CV VJG VQR KU VJG      EŽŶŵĞƚĂůůŝĐ   'ƌŽƵƉ ϭϳ
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                                                                                         ĚĞĐƌĞĂƐĞƐ
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          iodine (I) is the least nonmetallic                                             ŐƌŽƵƉ    ƌŽŵŝŶĞ ; ƌͿ
                                                                                                  /ŽĚŝŶĞ ;/Ϳ
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