Question

A nucleus that spontaneously decomposes is said to be.

Short answer

A nucleus that spontaneously decomposes is said to be undergoing radioactive decay or nuclear decay.

Step-by-step solution

Identifying the term for spontaneous decomposition of a nucleus

The phenomenon when a nucleus decomposes spontaneously is known as radioactive decay or nuclear decay.

Explaining radioactive decay

Radioactive decay is a random process where an unstable nucleus loses energy by emitting radiation or particles, typically alpha particles (α), beta particles (β), or gamma rays (γ). It is characterized by a predictable decay rate or half-life, which is the time it takes for half of a collection of identical nuclei to decay. Different elements have different half-lives, and their decay processes can change them into other, more stable elements. In summary, a nucleus that spontaneously decomposes is said to be undergoing radioactive decay or nuclear decay.

Key concepts

Nuclear Decomposition

Nuclear decomposition, also referred to as radioactive decay, involves a nucleus in an unstable state undergoing a transformation to become more stable. This transformation results in the emission of particles or radiation, leading to the eventual breakdown of the original atom into smaller parts.

Key points about nuclear decomposition include:

• It is a spontaneous process - meaning it occurs naturally without external influence.
• Once started, it continues until the atom reaches a stable state.
• This process can change the element to a different one due to the loss of protons or neutrons.

Through nuclear decomposition, elements may transform into entirely new elements with different properties. This presents rich avenues for further scientific inquiry and practical applications.

Half-Life

The concept of half-life is crucial in understanding radioactive decay. It is defined as the time required for half of the radioactive nuclei in a sample to decay into a more stable form.

Here's why half-life matters:

• It provides a measure of the rate of decay, allowing us to predict the longevity of a radioactive substance.
• By knowing the half-life, scientists can calculate the age of objects - this is widely used in carbon dating for archaeological findings.
• Different substances have varying half-lives - some are fractions of a second, while others span billions of years.

Half-life is a statistical measure and is not affected by external conditions such as temperature or pressure. Understanding it helps us grasp the stability and change processes within atoms.

Alpha Particle Emission

Alpha particle emission is one form of radioactive decay during which an unstable nucleus releases an alpha particle. An alpha particle consists of two protons and two neutrons, akin to a helium nucleus.

Important features of alpha particle emission:

• It causes a change in the original atom's mass and atomic number, decreasing the atomic number by 2 and the mass number by 4.
• This emission results in the formation of a new element that is positioned two places lower on the periodic table.
• Alpha particles have limited penetration ability, meaning they can be stopped by a sheet of paper or the outer layer of human skin.

Despite their weak penetration ability, alpha particles are highly ionizing and can cause significant damage if emitted inside the body.

Beta Particle Emission

Another facet of radioactive decay is beta particle emission, where an unstable nucleus emits a beta particle, either an electron or a positron.

When beta particles are emitted:

• Electrons are emitted during beta decay in neutron-rich nuclei, converting a neutron to a proton and increasing the atomic number by one.
• Positrons, which are positively charged electrons, are emitted from proton-rich nuclei, converting a proton to a neutron and decreasing the atomic number by one.
• Beta particles have a greater penetration ability than alpha particles but are still stopped by materials like plastic or thin metal sheets.

Beta decay is influential in changing the charge of the nucleus, thus altering the element's position in the periodic table. This process is critical in numerous applications, including medical treatments and dating of geological samples.

Gamma Rays

Gamma rays are a type of electromagnetic radiation emitted from the nucleus during radioactive decay. Unlike alpha and beta emissions, gamma rays do not consist of particles but rather high-energy photons.

Unique aspects of gamma rays include:

• They often follow alpha or beta decay and help the nucleus release excess energy.
• Gamma rays do not change the mass or atomic number of the element.
• Their high penetration ability requires dense materials like lead to block them effectively.

Gamma rays are the most penetrating and can potentially be harmful if not managed properly. Nonetheless, they have beneficial applications in medicine, such as cancer treatment, and in industrial settings for material inspection.