Answer:
Carbon 12 and 13 are carbon isotopes, meaning that they have additional neutrons:
Carbon 12 has exactly 6 protons and 6 neutrons ( hence the 12 )
Carbon 13 has 6 protons and 7 neutrons ( hence the 13 )
They differ in the number of neutrons in the nucleus.
Names:
carbon-13, C-13
carbon-12, C-12
