What type of particle is made up of two protons and two neutrons released from the nucleus of the radioactive atom?
It is an alpha particle.
Alpha decay causes the ejection of two protons and two neutrons from a parent nucleus. Alpha particles are essentially the nucleus of a helium atom. This results in not only a reduction in atomic mass by four, but also the number of protons (atomic number) by two in the daughter nucleus of the atom undergoing alpha decay, which changes the identity of the atom.