Answers

  • ATC
  • Ambitious
2015-01-30T21:54:41+05:30
In the periodic table there are groups-1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18
see in the group 1,2,13,14 the valancy is increasing like 1 2 3 4 and in groups 15,16,17,18 its decreasing like 4 3 2 1 0
18th is 0 valant -noble gases
1st group contains element with its outershell 1 like lithium whose congregation is 2,1 and 2 nd group has  magnesium with 2,8,2 and 14 th carbon valancy of 4-sharing
exclude groups-3 4 5 6 7 8 9 10 11 12 cauz it has mixed valancies.   
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2015-01-31T17:57:25+05:30
Valency of an element is determined by outermost shell of an atom
magnesium has its electronic configuration (2,8,2).
its outer most shell contains two electron so,it belongs to 2  group
and 3 period.

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