A) noble gases
B) halogens
C) heavy metals
D) light metals
Correct Answer: B
Solution :
The elements with atomic number 9, 17, 35, 53 and 85 are respectively \[F\], \[Cl\], \[Br\], \[I\]and At. These are VII A group elements which are also known as halogens (which means originating from sea). These also have 7 electrons in valence shell (i.e. \[n{{s}^{2}}n{{p}^{5}}\] ) e.g. \[_{8}F=1{{s}^{2}},2{{s}^{2}}2{{p}^{5}}\] \[_{17}Cl=1{{s}^{2}},2{{s}^{2}}2{{p}^{6}},3{{s}^{2}}3{{p}^{5}}\]
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