Problem 139 - A Complete Resource Book in Chemistry for JEE Main

Question

\(\beta\) particle is emitted in a radioactive reaction when (a) a proton changes to neutron (b) a neutron changes to proton (c) a neutron changes to electron (d) an electron changes to neutron

Step-by-Step Solution

Answer

Beta particle is emitted when a neutron changes to a proton (Option b).

Step 1: Understanding Beta Decay

Beta decay is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted from an atomic nucleus. During beta-minus (β-) decay, a neutron is transformed into a proton, an electron, and an antineutrino. This process increases the atomic number by one but keeps the mass number the same.

Step 2: Identifying the Correct Process

In beta-minus decay, a neutron in an unstable nucleus is converted into a proton, and a beta particle (an electron) along with an antineutrino is emitted. This conversion of neutron to proton facilitates the emission of a beta particle. Therefore, the correct process is when a neutron changes to a proton.

Step 3: Matching Options with Process

Reviewing the options provided: (a) a proton changes to neutron - Incorrect for β emission. (b) a neutron changes to proton - This is correct for β emission. (c) a neutron changes to electron - Incorrect, as it is not a process in nuclear reactions. (d) an electron changes to neutron - Incorrect, not a viable nuclear process.

Key Concepts

Radioactive Decay

Radioactive decay is a natural process by which an unstable atomic nucleus loses energy by emitting radiation. This radiation can come in the form of alpha particles, beta particles, or gamma rays. During radioactive decay, the nucleus changes from a higher energy state to a lower energy state.

There are various types of radioactive decay, but the common ones include alpha decay and beta decay. In alpha decay, the nucleus emits an alpha particle, which consists of 2 protons and 2 neutrons. This type of decay reduces the atomic mass and the atomic number of the element.

Beta decay, our primary focus, involves the transformation of neutrons or protons in the nucleus, leading to the emission of beta particles. Radioactive decay plays a crucial role in the natural transmutation of elements, changing them over time into different elements or isotopes:

• Transmutation of elements
• Emission of radiation
• Natural process of energy loss

Understanding these processes is key to illustrations of how certain elements transition from one form to another over long periods.

Beta Particle Emission

Beta particle emission is a fascinating phenomenon that occurs during certain types of radioactive decay, specifically beta decay. Beta particles can be either electrons or positrons emitted from the nucleus of an atom as a result of a nuclear transformation.

In beta-minus (b-) decay, the emitted beta particle is an electron. During this process, a neutron in the nucleus is converted into a proton, emitting an electron and an antineutrino. It's crucial to note that while the atomic number increases by one, the mass number remains unchanged, as the transformation involves subatomic particles:

• Electron emission from nucleus
• Increase in atomic number
• Mass number remains constant

Conversely, in beta-plus (b+) decay, a proton is converted into a neutron, emitting a positron and a neutrino, causing the atomic number to decrease while the mass number remains constant. Students often find beta decay a key point in understanding the changes occurring within an atom.

Neutron to Proton Conversion

The neutron-to-proton conversion is a core aspect of beta-minus decay. During this conversion, a neutron in the atom's nucleus transforms into a proton, an electron (which is the beta particle), and an antineutrino. This transformation is crucial as it leads to the emission of the beta particle, which is observed as emitted radiation.

This process not only influences the atomic structure but also leads to an increase in the atomic number by one. The atomic mass remains unchanged during this conversion because only a neutron changes to a proton:

• Neutron becomes a proton
• Emission of beta particle and antineutrino
• Atomic number increases

This neutron-to-proton conversion is vital in understanding nuclear reactions, particularly how unstable isotopes move towards a more stable state. It provides insight into the life cycle of radioactive elements and their transformation into other elements.