Question

Pockets of trapped helium gas are found near some deposits of radioactive ores. How can you explain this?

Short answer

The presence of trapped helium gas near deposits of radioactive ores can be explained by the alpha decay process of radioactive elements like uranium and thorium, which emit alpha particles. These alpha particles, composed of 2 protons and 2 neutrons, can pick up two electrons from their surroundings and become helium-4 atoms. Over time, the concentration of helium-4 atoms increases in the vicinity of the radioactive ores. Since helium is a light and inert gas, it can become trapped within pores and cracks in rocks or other materials, leading to pockets of trapped helium gas near radioactive ores.

Step-by-step solution

Understanding Helium Gas Properties

Helium is a noble gas and is the second lightest element in the periodic table. It is chemically inert, which means it does not react with other elements under normal conditions. Helium is formed during nuclear reactions, such as the ones occurring in the Sun and during radioactive decay of heavier elements.

Understanding Radioactive Decay

Radioactive decay is the process by which an unstable atomic nucleus loses energy by emitting radiation, such as alpha, beta, or gamma particles. Alpha particles, in particular, are composed of 2 protons and 2 neutrons, making them identical to helium-4 nuclei (the most common and stable isotope of helium). When certain unstable isotopes undergo alpha decay, they emit these alpha particles, which can pick up two electrons from surrounding materials and become a helium-4 atom.

The Formation of Helium Gas Near Radioactive Ores

When radioactive ores, such as uranium or thorium, undergo alpha decay, they emit alpha particles that can eventually become helium-4 atoms. Over time, as more and more isotopes decay, the helium-4 concentration in the vicinity of the radioactive ores increases. Because helium is an inert and light gas, it can become trapped within pores and cracks in rocks or other materials surrounding the radioactive deposit, leading to pockets of trapped helium gas.

Explaining the Presence of Helium Gas Near Radioactive Deposits

To summarize, the presence of trapped helium gas near deposits of radioactive ores can be explained as follows: 1. Radioactive ores, such as uranium and thorium, undergo alpha decay and emit alpha particles. 2. These alpha particles can become helium-4 atoms by picking up two electrons from surrounding materials. 3. Over time, the concentration of helium-4 atoms near the radioactive deposits increases. 4. Because helium is a light and inert gas, it can become trapped within pores and cracks in rocks or other materials, leading to pockets of trapped helium gas near radioactive ores.

Key concepts

Radioactive Decay

Radioactive decay represents the transformation that occurs within the nucleus of unstable atoms. These atoms spontaneously release energy as they seek stability through various types of decay, namely alpha, beta, and gamma. The process is governed by the laws of quantum mechanics and is not influenced by external conditions such as temperature or pressure.

Understanding radioactive decay is essential because it's responsible for the natural occurrence of certain elements, like helium, in the environment. Moreover, it has significant implications for fields ranging from archaeology, with carbon dating, to medicine, in cancer treatments with radiotherapy.

Alpha Particles

Alpha particles are a type of ionizing radiation ejected from the nuclei of certain radioactive elements during the process of alpha decay. These particles are essentially helium-4 nuclei, consisting of two protons and two neutrons, and carry a positive charge. When an unstable nucleus emits an alpha particle, it loses two protons and two neutrons, leading to a reduction in both atomic and mass numbers.

An alpha particle becomes a neutral helium atom once it captures two electrons from its surroundings, which can happen very quickly due to the particle's highly reactive nature owing to its charge.

Noble Gases

Noble gases such as helium, neon, and argon, occupy the far right column of the periodic table. These elements are characterized by their complete valence electron shells, making them extraordinarily stable and nonreactive under normal conditions. Helium gas does not easily combine with other elements, which is why it remains in its pure gaseous state when it is produced during radioactive decay.

The stability of noble gases has practical applications such as providing inert atmospheres for chemical reactions, in lighting technology, and as coolants in various applications due to their high stability.

Periodic Table

The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic numbers, electron configurations, and recurring chemical properties. Elements in the same column, or group, tend to share characteristics. For instance, the noble gases are found in Group 18. Understanding the layout of the periodic table is instrumental in chemistry because it helps predict the behavior of elements and how they might interact or transform, such as during radioactive decay.

Uranium and Thorium Isotopes

Uranium and thorium isotopes are heavy elements found naturally in various minerals. These isotopes are inherently unstable and undergo radioactive decay over time. As part of this decay, certain isotopes of uranium and thorium emit alpha particles and transform into lighter elements. With long half-lives, they are responsible for the sustained production of helium over geological time scales.

Both uranium and thorium are key in studying the age of rocks (geochronology) and understanding the heat production within the Earth, as their decay processes generate a significant amount of thermal energy.