The subscript giving the atomic number of an atom is often left off when writing an isotope symbol. For example, 6 often written simply as 13C. Why is this allowed?

Video transcript

Hello everyone today. We have the following problem when writing the ice a topic symbol of an element. The subscript representing the atomic number of the atom can be left off. For example, 18 has an atomic number of eight. However, Its weight is 18, so we write it as 18 with a as a superscript and oxygen for the symbol, which of the following statements explain why this is acceptable. So the answer here is because the atomic number of an atom can easily be found on the periodic table. If you look at a standard periodic table, the atomic number is going to be just to the top left of every box element. And so with that we've answered the question overall. I hope this helped and until next time.