Alpha particle An alpha particle is a subatomic particle that is made up of two protons and two neutrons. It is a helium nucleus: that is a helium atom without electrons. Radioactive elements give out alpha particles when they go through a kind of radioactive decay, known as alpha decay. During alpha decay, the atomic nucleus releases an alpha particle. The nucleus will lose two protons and two neutrons when this happens. After the decay, the atom will change to another element, because the atom loses two protons. For example, when plutonium goes through alpha decay it changes into uranium because it is defined to have two protons less than Plutonium. Alpha decay usually happens in heavy elements, those containing more neutrons and protons, such as uranium, thorium, plutonium, and radium. Alpha particles cannot even go through a few centimetres of air. Alpha radiation cannot hurt humans when the alpha source is outside the human body, because human skin does not let the alpha particles go through, it cannot penetrate it.

(SYMBOL fa OR He) An «-particle consists of two protons and two neutrons, 1.e. it is identical to a helium nucleus … consists of two protons (each of mass 1.007 28 u), two neutrons (each of mass 1.008 67 u) and two electrons … nucleus (5He) is produced (a) by fusing two neutrons and two protons, and (b) by fusing two deuterium nuclei

Ferromagnetic materials, such as iron, cobalt, and nickel, are strongly attracted to a magnetic field.[42] Radioactive decay Some elements, and many isotopes, have what is called an unstable nucleus. This means the nucleus is either too big to hold itself together, or it has too many protons or neutrons.[43] When a nucleus is unstable, it has to eliminate the excess mass of particles. It does this through radiation. An atom that does this is called radioactive. Unstable atoms emit radiation until they lose enough particles in the nucleus to become stable. All atoms above atomic number 82 (82 protons, lead) are radioactive.[44] There are three main kinds of radioactive decay: alpha, beta, and gamma.[25] - Alpha decay is when the atom shoots out a particle having two protons and two neutrons. This is a helium-4 nucleus. The result is an element with an atomic number of two less than before. So, for example, if a uranium atom (atomic number 92) went through alpha decay, it would become thorium (atomic number 90). Alpha decay happens when an atom is too big and needs to lose some mass. - Beta decay is when a neutron turns into a proton, or a proton turns into a neutron.