Give reasons for the following :
(i) Zn+2 salts are while but Cu2+ salts are blue in colour.
(ii) Fluorine gives only one oxide but chlorine gives a series of oxides.
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(i) Zinc and copper are transition metals and their ions are generally coloured due to d-d transition of unpaired electron.
But in case of Zn2+3d is completely filled and no unpaired electrons are available for transition. So light falling on these ions gets completely transmitted and their salts appear white. How ever ion Cu2+3d has 9 electrons. The unpaired electron absorbs particular wavelengths in visible region of light and the transmitted light shows the complementary colour 'blue'.
(ii) Fluorine has only two orbits. In 2nd orbit it has s2p5 configuration with no vacant 'd' orbitals. So it can not form more than one oxide i.e., OF2.
Chlorine, on the other hand, has 3 orbits in its atoms and 3d is lying vacant in it. Therefore it can show variable covalency and gives a series of oxides. Like Cl2O, ClO2.
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