Final answer:
Gamma rays are the type of radiation that have no mass and no charge, and they are a form of high-energy electromagnetic radiation. Unlike alpha particles and beta particles which have mass and charge, gamma rays can penetrate deeply through materials and are the least ionizing form of radiation.
Step-by-step explanation:
The type of radiation emitted by radioactive nuclei that has no mass and no charge is the gamma ray. Discovered by Ernest Rutherford, gamma rays, symbolized by the Greek letter gamma (γ), are a form of electromagnetic radiation like X-rays, but are more powerful. They are known for their high energy and deep penetration power, able to pass through various materials including human tissue. Gamma rays are considered to have the least ionizing power among the radiation types due to their lack of charge, but they can still ionize atoms indirectly through secondary processes.
Alpha particles, on the other hand, are composed of two protons and two neutrons, thus having a mass and a positive charge (+2). In contrast, beta particles are high-energy electrons with a negative charge (-1), which can be emitted from radioactive nuclei during beta decay. Positrons are the antiparticles of electrons, and they also have a mass and a positive charge. Therefore, out of the given options, gamma rays (A. gamma ray) are the only type of radiation that have neither mass nor charge.