The new type of radiation also aroused the interest of Ernest Rutherford. He first investigated the penetrating power of the radiation and was able to establish that it consisted of two components. He labelled them α and β radiation. He wrote:

These experiments show that uranium radiation is complex and that at least two different kinds of radiation occur - one which is absorbed very rapidly, called for convenience α-radiation, and the other, which has a more penetrating character, is called β-radiation (translation from Rutherford (1899)).

It was not long before a third component of radiation was identified. This was named γ-radiation in reference to the already known components. It can penetrate even deeper into matter than α and β radiation.

These properties of the types of radiation are summarised in the following table

In addition to the penetrating power of the individual types of radiation, further distinctions have been found. If the radiation is sent through an electric field, the α radiation is attracted to the negative pole and the β radiation to the positive pole. However, β-radiation is attracted more strongly than α-radiation. Similarly, the two types of radiation are also deflected in different directions in a magnetic field. However, γ-radiation is not influenced in either field.

The behaviour of the radiation in the electric and magnetic field shows that α-radiation must be positively charged and β-radiation must be negatively charged and both consist of particles. The strength of the deflection in the electric and magnetic field also made it possible to determine how heavy the particles are and how strongly they are charged.

β-particles are very light. They have almost no mass and are simply negatively charged. They behaved in the electric and magnetic field in exactly the same way as electrons, which J. J. Thomson had already discovered in 1897. This was a strong indication that β-radiation consists of electrons. They have a single negative charge and a mass of only 0.00055 u. This is 1800 times lighter than the lightest element, hydrogen.

α-particles are much heavier than β-particles. They have a mass of about 4 u. That is just as heavy as an atom of helium. However, the α-particles are doubly positively charged. It was therefore assumed that they are doubly positively charged helium atoms. Rutherford and his colleague T. Royds succeeded in proving this assumption in 1909.

γ-radiation, on the other hand, does not consist of particles, it carries no charge and is not deflected in an electric or magnetic field. It behaves in a similar way to the aforementioned X-rays. This radiation is pure electromagnetic radiation.