Page 49 - Science Class 08
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              More About Metals









               •  Noble Metals                     •  Non-metals                   •  Occurrence
               • Extrac on                         • Physical  roper es      P     • Chemical  roper es   P
               • Uses of  on-metals   N             • Alloys


              Any  chemical  element  that  is  an  effec ve         came  to  be  a  symbol  of  wealth.  Due  to  its
              conductor  of  electricity  and  heat  can  be        wonderful  quali es  and  its  luster,  gold  is
              defined  as  a  metal.  A  metal  is  also  good  at   considered  the  most  important  metal  in
              forming  bonds  and  ca ons  with  non-metals.        jewellery  making.  As  pure  gold  is  too  so   for
              Atoms inside of a metal quickly lose electrons        everyday  wear,  it  is  alloyed  with  a  mixture  of

              in order to make posi ve ions or ca ons. The          metals in order to make the gold harder, so it
              ions  in  turn  are  surrounded  by  the  electrons   can be used for jewellery.
              that  are  localised,  which  give  the  metal  its   During  the  Middle  Ages,  a  science  developed
              electric conduc vity.                                 that  aimed  at  making  gold  ar ficially.  This
                              NOBLE METALS                          science was named alchemy. Modern scien sts

              We have studied  in  the previous  chapter that       have  gained  success  in  extrac ng  gold  from
              gold is the least reac ve among all the metals.       sea-water and making ar ficial gold from lead
              So, it remains unaffected by air, water as well        and mercury. But, natural gold comes from the
              as acidic and alkaline substances. That is why it     earth only.
              is  mostly  found  in  pure  state.  Another  metal   Extrac on  :  Gold  is  mined  just  like  coal  a er
              —pla num also displays similar proper es. So,         drilling  deep  holes  in  rocks  using  explosives.
              these  two  metals  are  called  noble  metals.  A    When the rocks break, ores of gold are picked
              special  feature  of  these  metals  is  that  they
                                                                    up.  They  are  pounded  to  powdery  form  and
              maintain their lustre for long.
                                                                    then made into a pulp using water. This pulp is
              Let us read about them one-by-one:
                                                                    made into balls and fine par cles of gold (called
              Gold                                                  slime)  are  drained  off.  This  slime  is  put  into
              Gold  is  one  of  the  earliest  known  metals.  Its   cyanide solu on and zinc dust is used to make
              bright yellow colour is really so a rac ve that it    the gold in this solu on precipitate. Then, this

              Science-8                                                                                          49
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