Problem 28 - Chemistry The Central Science In Si Units

Question

In 1930 the American physicist Ernest Lawrence designed the first cyclotron in Berkeley, California. In 1937 Lawrence bombarded a molybdenum target with deuterium ions, producing for the first time an element not found in nature. What was this element? Starting with molybdenum-96 as your reactant, write a nuclear equation to represent this process.

Step-by-Step Solution

Answer

The element produced was technetium-97, represented in the equation \( ^{96}_{42}\text{Mo} + ^{2}_{1}\text{H} \rightarrow ^{97}_{43}\text{Tc} + ^{1}_{1}\text{p} \).

Step 1: Understand the Reactants

Start by identifying the reactants in the nuclear reaction. In this case, we need to write a nuclear equation starting with molybdenum-96 (Mo-96) bombarded by deuterium ions. Molybdenum-96 is denoted as \( ^{96}_{42}\text{Mo} \). Deuterium ions can be represented as \( ^{2}_{1}\text{H} \) because deuterium is an isotope of hydrogen with one neutron.

Step 2: Determine the Product and Its Formation

We know that the reaction produces an element not found in nature. When molybdenum-96 is bombarded with deuterium, a new element is formed through a (d,p) reaction, where a proton is emitted. Calculate the product: \( ^{96}_{42}\text{Mo} + ^{2}_{1}\text{H} \to ^{97}_{43}\text{Tc} + ^{1}_{1}\text{p} \). The new element, technetium-97 \( ^{97}_{43}\text{Tc} \), is produced.

Step 3: Write the Nuclear Equation

Assemble the nuclear equation using the reactants and products identified. The nuclear equation for this reaction is: \[ ^{96}_{42}\text{Mo} + ^{2}_{1}\text{H} \rightarrow ^{97}_{43}\text{Tc} + ^{1}_{1}\text{p} \] This equation shows molybdenum-96 reacting with deuterium to form technetium-97 and a proton.

Key Concepts

Nuclear Reactions

Nuclear reactions are fascinating interactions involving the nuclei of atoms. In these reactions, particles in the nucleus—protons and neutrons—are rearranged, leading to new elements or isotopes being formed. This is different from chemical reactions, which involve only the electrons surrounding an atom's nucleus.
There are a few common types of nuclear reactions:

• Alpha decay: Where an alpha particle (2 protons and 2 neutrons) is emitted from the nucleus.
• Beta decay: Involves the transformation of a neutron into a proton with the emission of an electron (or vice versa).
• Gamma decay: Energy is emitted from the nucleus in the form of gamma radiation, typically without the release of particles.
• Neutron capture: Neutrons are absorbed by a nucleus, often resulting in new isotopes.

Our scenario involves a specific nuclear reaction type called a (d,p) reaction. Here, deuterium (\( ^{2}_{1}\text{H} \)), an isotope of hydrogen, collides with molybdenum (\( ^{96}_{42}\text{Mo} \)). This interaction results in the ejection of a proton and the formation of a new element, technetium (\( ^{97}_{43}\text{Tc} \)). It's remarkable that nuclear reactions allow for the synthesis of elements not naturally found on Earth.

Element Synthesis

Element synthesis is an intriguing process where new chemical elements or isotopes are created. Unlike chemical processes which involve electron sharing or transfer, element synthesis deeply involves the nucleus of an atom. This process is usually carried out through nuclear reactions in particle accelerators, nuclear reactors, or during stellar processes.
In laboratories, scientists use devices like cyclotrons to bombard stable elements with particles like protons, neutrons, or heavier ions. When these particles strike the target nuclei, they can cause the nucleus to capture one of these particles, thereby transforming into a heavier element or a different isotope of the same element. The example at hand showcased element synthesis when Ernest Lawrence's cyclotron was used to bombard molybdenum with deuterium ions. The result was the creation of technetium, an element absent from the natural periodic table at the time. Such groundbreaking processes have led scientists to discover many transuranic elements, expanding our understanding of the periodic table beyond naturally occurring elements.

Cyclotron

The cyclotron is a type of particle accelerator, and it plays a critical role in nuclear chemistry, particularly in the field of element synthesis. Invented by Ernest Lawrence in the early 1930s, the cyclotron revolutionized nuclear physics by enabling the acceleration of charged particles to high speeds.
Here’s how it works:

• Circular Path: A cyclotron uses a strong magnetic field to force charged particles to travel in circular paths.
• Electromagnetic Acceleration: These particles are accelerated by a rapidly alternating electric field, which boosts their energy in each pass through the magnetic field.
• Target Impact: Once the particles reach a high enough speed, they collide with a target material—this is where nuclear reactions occur.

A cyclotron was pivotal in the discovery of technetium, as it allowed particles to have enough energy to induce nuclear reactions with molybdenum. The creation of particles at such high energies expanded opportunities for research into artificial elements and has myriad applications in both fundamental research and medical fields, such as in the production of medical isotopes used in diagnostic imaging.