Question

There are two elements-calcium (atomic number 20) and argon (atomic number 18). The mass number of both the elements is 40.  

They are therefore known as

(a) isotones 

(b) isochores

(c) isobars

(d) isotopes

Answer 1

(c) isobars

Isobars are atoms (nuclides) of different chemical elements that have same number of nucleons or mass number but different atomic number such as ⁴⁰Ca, ⁴⁰Ar.