The atomic number of calcium and argon are 20 and 18 respectively, but the mass number of both these elements is 40. Such pair is called:
Argon has atomic number of 18 and mass number of 40. Calcium has atomic 20 and mass number 40. Calcium and argon are examples of
An ion X2+ contains 18 electrons and 20 neutrons. Calculate the atomic number and mass no. of element X. Name the element X.