Question

Assertion: Atomic number is the number of protons present in the nucleus of an atom.

Reason: All atoms of an element have the same atomic number.

a. Both A and R are true and R is the correct explanation of assertion.

b. Both A and R are true but R is not the correct explanation of assertion.

c. A is true but R is false.

d. A is false but R is true.​

Answer 1

B is the answer
because atomic number of any element consists of same number of protons present in the nucleus of an atom


Reason :

Atoms of the same element have the same atomic number so the number of protons (and electrons) are same. But they have same or different mass number (like that for isotopes) . Different mass number will have different number of neutrons.