Subject :NSO Class : Class 9
A brief information about two atoms X and Y is given:
X : Atomic number = 7, Mass number = 14
Y : Atomic number = 7, Mass number = 15
Which of the following is correct about these two atoms?
A Electronic configuration of X is 2, 8, 4 while that of Y is 2, 8, 5.
B Both X and Y contain 7 neutrons.
C X has 2 electron shells while Y has 3 electron shells.
D Both X and Y have 5 valence electrons.
Answer should be (a)