QCM : Fundamentals of Radioactive Nuclei — 12 questions

Explication

A radioactive nucleus is defined as an unstable nucleus that undergoes spontaneous decay, emitting particles such as alpha, beta, or gamma radiation. The other options describe stable nuclei, artificially created nuclei, or nuclei with fixed neutron/proton numbers, which do not match the definition of a radioactive nucleus.

Explication

The standard notation for representing an atomic nucleus is with the mass number A as a superscript and the proton number Z as a subscript to the left of the element symbol X, written as A/Z/X. This notation clearly indicates the total nucleons and the number of protons, respectively. The correct option (index 1) correctly reflects this format. The other options either mix up the positions or use incorrect formatting.

Explication

Protons determine the element's identity because their number (Z) defines the atomic number, and they contribute to the nucleus's positive charge, which influences the atom's chemical behavior.

Explication

The correct sequence is alpha decay first, which reduces the mass number A by 4, followed by gamma emission, which releases energy without changing A, and then beta decay, which changes the atomic number but leaves A unchanged. This sequence reflects the typical order of decay processes in nuclear transformations involving A.

Explication

Isotopes are nuclei with the same number of protons (Z) but different numbers of neutrons, leading to different mass numbers (A). They are of the same element but differ in their nuclear composition, which distinguishes them from nuclei of different elements that have different Z.

Explication

Frederick Soddy is credited with proposing the concept of isotopes, recognizing that different nuclei could have the same number of protons but different neutron counts, which was a fundamental development in nuclear chemistry.

Explication

The emission of a positron during beta plus decay occurs because a proton in the nucleus is transformed into a neutron, and this process releases a positron (positon) along with a neutrino. This nuclear transformation is the cause of the positron emission.

Explication

In beta minus decay, the nucleus emits an electron, which is the particle to be detected to confirm this decay process. Positrons are emitted during beta plus decay, alpha particles during alpha decay, and gamma radiation is electromagnetic radiation emitted during various decay processes but is not specific to beta minus decay.

Explication

Alpha decay particles are helium nuclei, composed of 2 protons and 2 neutrons, which makes them distinct from other particles like electrons, protons, or gamma rays emitted during different types of decay.

Explication

Gamma radiation is high-energy electromagnetic radiation emitted during radioactive decay, often accompanying particle emissions, and capable of ionizing matter.

Explication

Gamma rays are high-energy electromagnetic radiation emitted during radioactive decay, and they are capable of ionizing atoms and molecules and penetrating matter. This distinguishes them from alpha and beta particles, which are particles with mass and charge.

Explication

Radioactive activity measures the number of disintegrations occurring per second in a sample, which indicates how quickly the nucleus is decaying. It is expressed in Becquerel (Bq) and is fundamental for assessing the stability of radioactive materials and their potential hazards.