The statement that a beta particle is a mass-less particle with an atomic number of -1 is not accurate. In fact, beta particles do have mass and a charge, but their specific properties depend on whether they are beta-minus (β-) particles or beta-plus (β+) particles.
A beta-minus particle, commonly referred to as an electron, has a negative charge and a mass that is approximately 1/1836 times that of a proton. It is denoted as β- and is emitted during certain types of radioactive decay, such as beta decay.
On the other hand, a beta-plus particle, also known as a positron, has a positive charge and the same mass as an electron. It is denoted as β+ and is also emitted during certain types of radioactive decay, specifically positron emission.
These properties of beta particles, including their charge and non-zero mass, have been extensively studied and experimentally verified through various methods. Techniques such as cloud chamber experiments, which allow the visualization of particle tracks, and measurements of the momentum and energy of beta particles, confirm their existence as charged particles with mass.
In summary, beta particles do have mass, and they carry a charge. They are not mass-less particles with an atomic number of -1.