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प्रश्न
Which of the given elements A, B, C, D and E with atomic number 2, 3, 7, 10 and 30 respectively belong to the same period?
विकल्प
A, B, C
B, C, D
A, D, E
A, D, E
उत्तर
B, C, D
Explanation -
Electronic configuration of A = 2
Electronic configuration of B = 2,1
Electronic configuration of C = 2,5
Electronic configuration of D = 2,8
Electronic configuration of E = 2,8,8,8,4
If the electronic configuration of the given elements is written, only elements B, C and D have electrons occupying only two shells. So, only elements B, C and D would be placed in the same period in the modern periodic table.
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