Question

Which corner of the isotope symbol contains the mass number?

Answer 1

The top left corner, as we read the symbol on the page.

Explanation:

When we write `""^12""_6C`, the bottom left symbol is the atomic number `Z`; the top left smbol is the mass number. Since the elemental symbol, the `C`, automatically specifies the atomic number `Z=6`, it is redundant, and may be discarded to give just `""^12C`. Reading this symbol, this tells us that we deal with a nucleon with 6 neutrons in the nucleus, 6 massive, neutrally charged, nucular particles.

For the `""^13C` and `""^14C` isotopes, how many neutrons in each such atom? And how many electrons? Why?