1.

the electronic configuration of an atom is K^2 L^7.if there are 10 neutrons in the atom,its mass number is options are 28,19,10 and 9

Answer»

No. of ELECTRONS in 'K' shell = 2

No. of electrons in 'L' shell = 7

THEREFORE, ATOMIC NUMBER = TOTAL NUMBER OF ELECTRONS

                                                      = 2 + 7 = 9

No. of Neutrons = Mass Number - Atomic Number

10 = Mass number - 9

Mass number = 10 + 9 = 19

Correct option is (B).

HOPE  IT  HELPS!!!!



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