Video Transcript
Nuclide notation is used to represent different types of ionizing radiation. Which type of ionizing radiation is represented by the nuclide notation four two He? (A) Gamma rays, (B) beta particles, (C) X-rays, or (D) alpha particles.
Ionizing radiation is radiation that carries enough energy to remove electrons from atoms. Not all radiation is ionizing. For example, visible light, radio waves, microwaves, and infrared are all nonionizing. All of the options we’ve been given from (A) to (D) are types of ionizing radiation. The nuclide notation we have been given is four two He. In nuclide notation, the top-left number, which in this case is four, is the mass number. It tells us the total number of protons and neutrons. The bottom-left number, which in this case is two, is the atomic number, which tells us the number of protons.
Option (A) is gamma rays. Gamma radiation produces gamma rays. They are short-wavelength, high-frequency electromagnetic waves. Gamma rays don’t contain protons and neutrons. Its nuclide notation is zero zero and the Greek letter 𝛾. It is not represented by four two He. So we know that option (A) gamma rays is not the answer to this question.
Option (B) is beta particles. Beta particles are emitted during beta decay, of which there are two types: 𝛽− decay and 𝛽+ decay. A beta particle is a high-energy electron or positron, where a positron is an antiparticle to the electron. During 𝛽− decay, a neutron is converted to a proton releasing an electron and an antineutrino. In the nucleus undergoing decay, the atomic number would increase by one as the number of protons had increased by one, but the mass number would stay the same as the total number of protons and neutrons is unchanged. To balance the increase in atomic number of the nucleus, the symbol given for 𝛽− decay has a minus one as the atomic number. The nuclide notation is zero minus one 𝛽 or sometimes zero minus one e.
In 𝛽+ decay, a proton is converted to a neutron, releasing a positron and neutrino. To balance out the decrease in atomic number in the nucleus that’s undergone decay, the nuclide notation has a plus one as the atomic number, so the symbol is zero plus one 𝛽 or zero plus one e. None of these symbols match the symbol given in the question, four two He. So option (B), beta particles, cannot be the answer to this question.
Option (C) is X-rays. Like gamma rays, X-rays are part of the electromagnetic spectrum. They do not contain protons and neutrons and do not have mass. So it cannot be the answer to this question. Additionally, they’re not emitted from the nucleus, so do not have nuclide notation.
Option (D) is alpha particles. Alpha particles are emitted during alpha decay. An alpha particle consists of a helium nucleus. A helium nucleus consists of two protons and two neutrons. Thus, it would have a mass number of four as the total number of protons and neutrons is four, an atomic number of two as it contains two protons, and the chemical symbol for helium is He. So the answer to the question “Which type of ionizing radiation is represented by the nuclear notation four two He?” is (D) alpha particles.