Question

which of the following cannot be emitted in radioactive decay of the substance? (A) Helium-nucleus (B) Electrons (C) Neutrinos (D) Proton.

Short answer

In conclusion, the particle that cannot be emitted in radioactive decay of the substance is the Proton (D).

Step-by-step solution

Helium-nucleus

Helium-nucleus, also known as an alpha particle, consists of 2 protons and 2 neutrons. It is a common particle emitted during radioactive decay, especially in heavy elements like uranium or plutonium. An unstable nucleus emits an alpha particle to reduce its mass and become more stable. So, a Helium-nucleus can be emitted in radioactive decay.

Electrons

Electrons can be emitted during a type of radioactive decay known as beta decay. In beta-minus decay, a neutron in the nucleus transforms into a proton, releasing an electron (beta particle) and an electron-antineutrino. In beta-plus decay or electron capture, a proton in the nucleus transforms into a neutron, releasing a positron (anti-electron) and an electron-neutrino. Therefore, electrons can also be emitted in radioactive decay.

Neutrinos

Neutrinos are elusive, nearly massless particles that travel at nearly the speed of light. They are emitted during beta decay, as mentioned previously. In beta-minus decay, an electron-antineutrino is released alongside the electron. In beta-plus decay, an electron-neutrino is released along with the positron. Thus, neutrinos can be emitted in radioactive decay.

Proton

Protons are positively charged particles found in the nucleus of an atom. Generally, protons are not emitted alone during radioactive decay processes, such as alpha or beta decay. In fact, the only known process for a single proton to be emitted from a nucleus is known as proton emission. However, proton emission is a rare type of radioactive decay that only occurs in a few specific conditions, such as in extremely proton-rich isotopes. In comparison to alpha, beta, and gamma decay, proton emission is not a common process. Thus, (D) Proton is the correct answer, as it is rarely emitted in radioactive decay. In conclusion, the particle that cannot be emitted in radioactive decay of the substance is the Proton (D).

Key concepts

Alpha Decay

Radioactive decay is a fascinating process where an unstable atomic nucleus loses energy by radiation. One well-known type of decay is alpha decay. During alpha decay, the unstable nucleus releases an alpha particle.

Alpha particles are made up of 2 protons and 2 neutrons. This essentially forms a helium nucleus. Alpha decay typically happens in heavy elements like uranium and plutonium.

This process helps an unstable nucleus become more stable by reducing its overall mass.

When the nucleus emits an alpha particle:

• The atomic number decreases by 2.
• The mass number decreases by 4.

Understanding alpha decay allows scientists to grasp why certain elements change their identities over time, often transforming into entirely different elements. This principle is crucial in various applications, such as nuclear energy and radiometric dating.

Beta Decay

Beta decay is another intriguing type of radioactive decay whereby an unstable nucleus emits a beta particle. Beta particles can be either electrons or positrons, and this process affects the atomic structure in different ways.

There are two types of beta decay:

• Beta-minus decay: A neutron in the nucleus transforms into a proton. This release involves an electron (beta particle) and an electron-antineutrino.
• Beta-plus decay: A proton in the nucleus transforms into a neutron, resulting in the emission of a positron and an electron-neutrino.

In beta-minus decay:

• The atomic number increases by 1.

In beta-plus decay:

• The atomic number decreases by 1.

Beta decay is significant because it alters the number of protons in the nucleus, causing the element to "transmute" into another element. This has important implications in areas like medicine, particularly in PET scans that utilize positrons.

Neutrinos

Neutrinos are tiny, nearly massless particles that play a role in particle decay processes, including beta decay.

They are known for barely interacting with other matter because of their neutral charge and minuscule mass, allowing them to travel through vast amounts of material without being affected.

During radioactive decay, neutrinos are often emitted:

• In beta-minus decay, an electron-antineutrino accompanies the electron emission.
• In beta-plus decay, an electron-neutrino is emitted along with the positron.

Despite being hard to detect, neutrinos provide valuable insights into the fundamental workings of particles and forces in physics. Their study has led to major advances in our understanding of the universe, particularly in particle physics.

Proton Emission

Proton emission is a rare kind of radioactive decay compared to alpha and beta decays. During this process, a nucleus ejects a single proton.

This usually happens in rare cases involving proton-rich isotopes, which means there are more protons than needed for stability.

Proton emission is less common than other forms of decay, such as alpha and beta decay. It's a fascinating process, mostly studied in theoretical and experimental nuclear physics to understand the limits of nuclear stability.

Unlike the other decay types, proton emission doesn’t change the mass significantly but does reduce the proton number by one:

• This results in the transformation to a new element with a lower atomic number.

Understanding proton emission is key in exploring nuclear reactions and the structure of exotic nuclei, broadening perspectives about atomic interactions beyond the common isotopes.