Atomic mass: The standard atomic weight of an element is the average mass of the element written in atomic mass units (amu). Even though each atom has roughly a whole number of atomic mass units, ...

For example, you may have a card that says that the atom you are looking for has 5 neutrons. You would look at the periodic table to find an atom that you could add 5 to its number of protons that ...

Manvendra memorised each element’s name, atomic number, and atomic mass, accurate to two decimal places, and recited them ...

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 ...