Two different naturally occurring atoms of carbon can be represented as 612C{}^{12}_{6}\text{C}612C and 614C{}^{14}_{6}\text{C}614C.
Complete the sentences below using the correct words or phrases from the list:
These atoms of carbon are called (i) ________
because their (ii) ________ are the same,
but their (iii) ________ are different.
