there is mistake in your video lecture of ch structure of the atom
If we see the atomic structure of helium. In which no of proton=2 and no of neutron=2 and no of electrons=2. If we remove the two electrons from the atoms of helium. Helium will get the 2 positive charge due to presence of two protons in the atom with atomic mass 4 which is equal to alpha particles. Alpha particles also have the two positive charge with atomic mass 4(Atomic mass = no. of proton+ no. of neutrons).So we can also represent the alpha particle He²⁺. It has the only two positive charges with 4 atomic mass.