an atom contains a very small nucleus composed of positively charged protons and uncharged neutrons

the nucleus contains the majority of an atoms mass because protons and neutrons are much heavier than electrons

atomic mass unit (amu) fundamental unit of charge (e)

any atom that contains six protons is the element carbon and has the atomic number 6

The total number of protons and neutrons in an atom is called its mass number (A)

An atom that gains one or more electrons will exhibit a negative charge and is called an anion.