A radioactive substance can emit several kinds of nuclear radiation. Which option correctly describes the main types of particles and rays that may be emitted during radioactive decay?

Introduction / Context:
Radioactivity is the spontaneous emission of radiation from unstable atomic nuclei. In basic nuclear chemistry and physics, students learn about three main traditional types of radiation: alpha, beta, and gamma. Examination questions often test whether you can recall these types and recognise that radioactive substances may emit one or more of them. This question asks which combination of radiations is associated with radioactive decay in general.

Given Data / Assumptions:

• Radioactive nuclei may undergo different decay modes, such as alpha decay, beta decay, and gamma emission.
• Alpha particles are helium nuclei, beta particles are high energy electrons or positrons, and gamma rays are high energy electromagnetic radiation.
• Not every radionuclide emits all three types, but the question is about the main types associated with radioactivity in general.
• Neutron emission exists but is not among the basic three types introduced at school level.

Concept / Approach:
Traditional descriptions of radioactivity emphasise three principal forms of radiation: alpha (α), beta (β), and gamma (γ). Alpha particles are heavy, positively charged, and have low penetration. Beta particles are lighter, negatively charged or positively charged, with moderate penetration. Gamma rays are neutral, highly penetrating electromagnetic waves that often accompany alpha or beta decay. A radioactive substance may emit any one of these or a combination, but when a general question lists alpha, beta, and gamma as options, the inclusive answer is that all three may be emitted by radioactive substances.

Step-by-Step Solution:
Step 1: Recall that alpha radiation consists of helium nuclei, two protons and two neutrons, emitted from heavy nuclei. Step 2: Recall that beta radiation consists of high energy electrons or positrons emitted when a neutron converts to a proton or vice versa. Step 3: Recall that gamma radiation is a high energy photon emitted when the nucleus moves from an excited state to a lower energy state. Step 4: Recognise that standard nuclear chemistry teaching presents all three as characteristic of radioactive decay processes. Step 5: Choose the option that mentions all three types together as the radiations a radioactive substance may emit.

Verification / Alternative check:
Examples include uranium and thorium series nuclei that emit alpha particles as they decay through chains, beta emitters like carbon-14 used in radiocarbon dating, and gamma emitters used in medical imaging and therapy. Many decay schemes show a sequence where alpha or beta emission changes the nucleus, followed by gamma emission as the nucleus loses extra energy. Radiation safety guidelines always refer to alpha, beta, and gamma as the primary categories that must be shielded or monitored. This confirms that all three are recognised as main types of radioactive emission.

Why Other Options Are Wrong:
Saying that only alpha, only beta, or only gamma radiation is emitted ignores the variety of decay modes observed in nature and technology. While some nuclides are pure beta emitters or predominantly alpha emitters, radioactivity as a whole cannot be reduced to a single radiation type. The option that mentions neutrons only is incomplete and not representative of typical school level classification, because neutrons are not counted as one of the three basic radiations introduced to beginners.

Common Pitfalls:
A common mistake is to pick alpha or beta alone because these are often the first types discussed in class, forgetting the presence of gamma rays. Another pitfall is to think that gamma rays are secondary and do not count as radiation emitted by the substance, which is not correct. To avoid errors, memorise that radioactive decay is associated with three principal radiations: alpha particles, beta particles, and gamma rays, and remember that the safest inclusive answer is usually the one mentioning all three.

Final Answer:
A radioactive substance may emit all three main types of radiation: alpha particles, beta particles, and gamma rays.