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 ...

He lived, worked, and died there ... Bohr began to work on the problem of the atom's structure. Ernest Rutherford had recently suggested the atom had a miniature, dense nucleus surrounded by ...

The atom is neutral as it has two positive protons and two negative electrons. A helium atom that has lost or gained an electron is an ion. The ion has two positive protons but one electron so it ...

It is not the same as a helium atom as it does not contain any electrons but it is written with the same chemical nomenclature as a helium atom: \(_{2}^{4}\textrm{He}\) When a radioactive atom ...