Final answer:
The statement that is not true about beta radiation is that it is the heaviest of the three types. Alpha particles are heavier than beta particles. Beta radiation consists of high-speed electrons or positrons and results in an increase in the atomic number without changing the mass number.
Step-by-step explanation:
The statement about beta radiation that is not true is "D) It is the heaviest of the three types." Alpha radiation is actually the heaviest type because it consists of helium nuclei, which are made of two protons and two neutrons. In contrast, beta radiation consists of beta particles, which are high-energy, high-speed electrons or positrons here referred to as beta particles (e-0). These particles are definitely not heavier than alpha particles.
When a beta particle is emitted from the nucleus during beta decay, it causes the transformation of a neutron into a proton. This process increases the atomic number of the element by one, but the mass number remains the same because the beta particle itself does not contribute significantly to the mass of the atom.
The beta particles have a negative charge, and their emission does lead to transmutation, as the identity of the element changes due to the increase in the atomic number.