Question

A and B are two elements which have same atomic weight and are having atomic number 27 and 30 respectively. If the atomic weight of A is 57 then number of neutron in B is :

• A. 27
• B. 33
• C. 30
• D. 40

Answer 1

The correct option is A 27

A and B are two elements which have same atomic weight and are having atomic number 27 and 30 respectively. If the atomic weight of A is 57 then number of neutron in B is 27.
The atomic weight of B is equal to the atomic weight of A. It is equal to 57.
The atomic mass of B is 30.
The number of neutrons in B is $57-30=27$.