Question

Bombarding Br- 81 with gamma rays gives a radioactive nuclide and a neutron. Identify the radionuclide.

Short answer

The radionuclide formed is bromine-80 (\(^{80}Br\)).

Step-by-step solution

Understand the Reaction

Bombarding a stable isotope, bromine-81, with gamma rays typically creates an excited state of the nucleus. Gamma rays do not change the atomic number or mass number, meaning the atomic number (Z) remains 35 and the mass number (A) remains 81 initially.

Identify the Changes

The excitation of the nucleus may cause a neutron (n) to be emitted. This results in a decrease in the mass number by 1, as emitting a neutron changes the isotope to a new element whose mass number is 80, while the atomic number remains the same.

Write the Nuclear Equation

The nuclear reaction can be written as: \[ _{35}^{81}Br + \gamma \rightarrow _{35}^{80}Br + _0^1n \] The emission of a neutron from \(_{35}^{81}Br\) gives a new nuclide \(_{35}^{80}Br\).

Confirm the Reaction Product

Since the mass number decreases by one (from 81 to 80) and the atomic number remains unchanged, the radionuclide formed is \(_{35}^{80}Br\), which is the isotope of bromine with mass number 80.

Key concepts

Radioactive Decay

Radioactive decay is a natural process by which the nucleus of an unstable atom loses energy by emitting radiation. This can include various particles or electromagnetic waves. Unstable nuclei tend to undergo decay in order to reach a more stable, lower energy state.

There are several types of radioactive decay, such as:

• Alpha decay: The nucleus emits an alpha particle, consisting of 2 protons and 2 neutrons.
• Beta decay: The process involves the transformation of a neutron into a proton (or vice versa), resulting in the emission of beta particles, which are electrons or positrons.
• Gamma decay: The nucleus moves to a lower energy state by emitting gamma rays. This process doesn't alter the mass number or the atomic number.

Gamma decay is particularly relevant in the process described here, as the exercise involves bombarding bromine-81 with gamma rays, leading to the emission of a neutron.

Gamma Radiation

Gamma radiation is a form of electromagnetic radiation, similar in nature to X-rays, but with higher energy. They are the product of radioactive atoms undergoing nuclear reactions to reach a more stable state.

Characteristics of Gamma Radiation:

• Gamma rays have no mass and no charge, which means they influence the energy state of the nucleus but do not alter the atomic or mass numbers when they interact with atoms.
• They are highly penetrating and require dense materials like lead for effective shielding.

In the exercise, when bromine-81 is bombarded with gamma rays, the nucleus of bromine enters an excited state. This state can lead to the emission of a neutron, effectively altering the isotope to bromine-80 while the atomic number remains unchanged.

Nuclear Reactions

Nuclear reactions involve changes in the nucleus of an atom. These reactions can result in the conversion of one element to another, a new isotope, or an entirely different composition.

Types of Nuclear Reactions:

• Fusion: Light nuclei combine to form a heavier nucleus, releasing energy.
• Fission: A heavy nucleus splits into two smaller nuclei, along with several neutrons and energy.
• Transmutation: One element changes into another, often involving particle interactions.

In the provided exercise, bombarding bromine-81 with gamma rays is a type of transmutation. The excited state resulting from gamma-ray interaction allows a neutron to be emitted, changing bromine-81 to bromine-80 without altering the atomic number. This demonstrates how nuclear reactions can result in the formation of new isotopes and elements, by altering nuclear structure.