I’ve seen several people on message boards and comment sections on the internet state that helium cannot decay into lithium. These folks don’t know what they are talking about. They do not understand beta decay.
Beta decay: Beta particles are electrons or positrons (electrons with positive electric charge, or anti-electrons). Beta decay occurs when, in a nucleus with too many protons or too many neutrons, one of the protons or neutrons is transformed into the other. In beta minus decay, a neutron decays into a proton, an electron, and an anti-neutrino: n Æ p + e – +. In beta plus decay, a proton decays into a neutron, a positron, and a neutrino: p Æ n + e+ +n. Both reactions occur because in different regions of the Chart of the Nuclides, one or the other will move the product closer to the region of stability. These particular reactions take place because conservation laws are obeyed. Electric charge conservation requires that if an electrically neutral neutron becomes a positively charged proton, an electrically negative particle (in this case, an electron) must also be produced. Similarly, conservation of lepton number requires that if a neutron (lepton number = 0) decays into a proton (lepton number = 0) and an electron (lepton number = 1), a particle with a lepton number of -1 (in this case an antineutrino) must also be produced. The leptons emitted in beta decay did not exist in the nucleus before the decay–they are created at the instant of the decay.
The nucleus is composed of protons (charge = +1; mass = 1.007 atomic mass units ([μ]) and neutrons. The number of protons in the nucleus is called the atomic number (Z) and defines which chemical element the nucleus represents. In beta minus decay a neutron decays into a proton, an electron, and an anti-neutrino. This changes the chemical element that the nucleus represents and the nucleus moves up one element on the periodic table.
As we see in the chart below from Wikipedia helium-6 and helium-8 do indeed decay into lithium:
Although some helium isotopes, such as 6He and 8He, decay mostly to isotopes of lithium, the major tendency among known isotopes seems to be decay into lighter helium isotopes. Fission, seen only in even-numbered isotopes, is also unusually common.
Decay chains for isotopes with multiple decay modes listed in order of probability.