Different atoms of chlorine can be represented as 1735Cl{}^{35}_{17}\text{Cl}1735Cl and 1737Cl{}^{37}_{17}\text{Cl}1737Cl.
Complete the sentences below using the correct words or phrases from the list:
These atoms of chlorine are called (i) ________ because their (ii) ________ are the same, but their (iii) ________ are different.