For example, the mass number of both argon atoms and calcium atoms is 40. The atomic number of a sodium atom is 11 and its mass number is 23. Calculate the number of protons, neutrons and ...

But remember, there are no electrons inside the nucleus. This is the chemical symbol for chlorine, written with its mass number and atomic number. Calculate the number of protons, neutrons and ...

Scientists use the periodic table to quickly refer to information about an element, like atomic mass and chemical symbol. The periodic table’s arrangement also allows scientists to discern trends in ...

For example, a helium atom has an atomic mass of 4, but an atomic number (or positive charge) of 2. Since electrons have almost no mass, it seemed that something besides the protons in the nucleus ...