The chemical nature of the alpha particles from radioactive substances

The lecture surveys experimental study of alpha radiation, tracing early observations that separated α, β, and γ rays and describing experiments demonstrating that α-rays consist of positively charged, massive particles. It explains magnetic and electric deflection measurements that yielded particle velocities and charge-to-mass ratios indicating a mass about twice that of hydrogen and suggests the α-particle may be a helium or hydrogen atom. The results are placed in the context of the emerging transformation theory of radioactivity, arguing that emission of α-particles produces successive distinct radioactive substances that decay according to definite laws.