Problem 77 - Chemistry The Molecular Nature of Matter

Question

Gamma-ray bombardment of bromine-81 causes a transmutation in which a neutron is one product. Write the symbol of the other product.

Step-by-Step Solution

Answer

The symbol of the other product is \( ^{80}_{35}\text{Br} \).

Step 1: Understand the Transmutation Process

Transmutation occurs when an atom's nucleus is changed due to nuclear reactions, which often involves particles being ejected or absorbed. In this case, gamma-ray bombardment causes a neutron to be ejected. Therefore, a neutron being one product implies that the atomic mass will decrease by one unit.

Step 2: Identify the Original and Final Nuclide

Bromine-81 (with an atomic number of 35) loses a neutron due to bombardment. The loss of a neutron decreases its mass number to 80, but the atomic number remains unchanged because it is losing a neutron, not a proton.

Step 3: Write the Symbol for the Resulting Nuclide

The resulting nuclide will still be bromine, because the atomic number is still 35, but its mass number will now be 80, denoted as \( ^{80}_{35}\text{Br} \).

Key Concepts

Gamma-Ray Bombardment

Atomic nuclei can be transformed through various processes, one of which involves gamma-ray bombardment. Gamma rays, which are high-energy photons, can induce reactions when they collide with nuclei. During such a collision, gamma rays can transfer sufficient energy to eject particles from the nucleus, leading to a change in the structure or energy state of the nucleus.

When a stable nuclide such as bromine-81 absorbs a gamma photon, the gamma-ray's energy adds to the nucleus, causing instability. The nucleus then releases this excess energy by ejecting a neutron, thus changing the composition of the atom in a process known as nuclear transmutation. Understanding this concept is key to grasping the nuances of nuclear chemistry and the many applications that require precise manipulation of nuclear states, from medical treatments to energy production.

Neutron Ejection

The process of a nucleus releasing a neutron is a significant nuclear event. Neutron ejection results in a decrease in the atomic mass number by one, because neutrons contribute to the mass of an atom but have no charge. This means the chemical element does not change since the atomic number, which defines the element, remains the same.

Nuclear reactors and certain research experiments often leverage neutron ejection phenomena to produce isotopes or to study the structure of atomic nuclei. For instance, when a stable isotope such as bromine-81 undergoes neutron ejection, the neutron itself can be detected and analyzed as one of the products of the reaction, providing insight into the behavior of atomic particles under extreme conditions. This process is integral to our understanding of nuclear physics and chemistry.

Nuclide Notation

Nuclide notation is a shorthand way of expressing information about specific isotopes of elements. It includes the element's symbol, as found on the periodic table, and two numbers which denote the atomic number and mass number of the isotope. The mass number, representing the total count of protons plus neutrons, is written as a superscript to the left of the element symbol. The atomic number, indicating the number of protons and also the element's identity, is written as a subscript.

For example, bromine with a mass number of 80 and an atomic number of 35 is written as \( ^{80}_{35}\text{Br} \). By utilizing nuclide notation, chemists and physicists can quickly convey detailed information about the structure of an atom, which is essential when discussing nuclear transmutations and other nuclear phenomena.