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 ...

Normal helium, which is 700,000 times more common than helium-3, is called helium-4 because it has two protons and two neutrons. Whereas helium-4 is a common product of the decay of radioactive ...

A helium atom has two electrons in an energy level outside the nucleus. The atom is neutral as it has two positive protons and two negative electrons. A helium atom that has lost or gained an ...

An alpha particle is also a helium-4 nucleus, so it is written as \(_{2 ... not the outside of the atom. Electrons are not normally expected to be found in the nucleus but neutrons can split ...