Question

Naturally occurring nitrogen has two isotopes N-14 and N-15. Which isotope has greater number of electrons?

Answer 1

Isotopes are those elements which have same number of proton but different mass number, that is, there is a change in number of neutrons.

Now, since they have same number of proton, then the number of electron would also be the same because we know that atom as a whole is neutral.

Hence, N-14 and N-15 would have same number of electrons.

Answer 2

Isotopes

Atom of the same element having different mass number. The mass number are different due to difference in number of neutrons.

For example :- C-12 and C-14 are two isotopes of carbon. C-12 has 6 neutrons while C-14 has 8.Also,since atomic number of carbon is 6, they both have 6 protons.They are neutral too, hence they will have 6 electrons. This implies that :-

Isotopes have equal number of electrons.

Solutions:-

We have seen that isotopes have equal number of electrons, hence N-14 and N-15 has equal number of electrons.

Additional information

Sometime, atomic mass of two isotopes of an element is given and average atomic mass is asked , we solve them using the following procedure :-

Que:- Find average atomic mass of N when its two isotopes are N-14 and N-15 when N contains x % of N-14.

Soln:- Let N contains x % of N-14 and (100 - x)℅ of N-15. Hence, average atomic mass will be given by

14 × x℅ + 15 × (100 - x)℅

=> 14x/100 + (1500 - 15x)/100

=> (1500 - x)/100