I was reading Silberberg's principles of general chemistry when I noticed that it says that the mass of carbon12 is exactly 12 amu. But when I calculated the total mass of its components (6 protons : 1.00727 amu each , 6 neutrons : 1.00866 amu each and 6 electrons : 0.000548 amu each) it was obviously greater than 12. Why is that?

My explanation was that some of the mass is converted to energy but I don't know whether it was true or not.

And I'm sorry if my English is not good.


marked as duplicate by DavePhD, jerepierre, bon, Todd Minehardt, ringo Oct 27 '16 at 23:46

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • 2
    $\begingroup$ That's right: when you put together 6 protons, 6 neutrons, and 6 (not 12, mind you) electrons, some of the mass will be lost as energy. Also, your English is fine. Also, welcome to Chem. SE. $\endgroup$ – Ivan Neretin Oct 27 '16 at 7:39
  • $\begingroup$ Sorry for the mistake (12 electrons) and thanks for your answer Ivan Neretin. $\endgroup$ – Ali Oct 27 '16 at 7:45

Browse other questions tagged or ask your own question.