Problem 28 - Chemistry: The Central Science in SI Units, Global Edition

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 by Ernest Lawrence when he bombarded a molybdenum target with deuterium ions is Technetium. The nuclear equation representing this process is: \(^{96}_{42} Mo + ^{2}_{1}D \rightarrow ^{98}_{43}Tc\).

Step 1: Identify the reactants

In this nuclear reaction, we have two reactants: - Molybdenum-96 (\(^{96}_{42} Mo\)) - Deuterium (\(^{2}_{1}D\ or\ ^{2}_{1}H\)) Step 2: Determine the deuterium ion

Step 2: Determine the deuterium ion

Since deuterium has one proton and one neutron, its atomic number is 1, and its mass number is 2. Recall that a deuterium ion is a deuterium atom that has lost its electron and therefore has a +1 charge. However, when writing nuclear equations, we don't need to consider the charges. Step 3: Determine the initial element

Step 3: Determine the initial element

This exercise states that we start with molybdenum-96 as the reactant. Molybdenum has an atomic number of 42 and a mass number of 96, so it is represented as \(^{96}_{42} Mo\). Step 4: Write the nuclear reaction formula

Step 4: Write the nuclear reaction formula

A nuclear reaction involves changes in the nucleus of an atom. When molybdenum-96 is bombarded with deuterium, a new element is formed. In this case, we don't know the identity of the new element, so we can represent it using X. To balance the equation, we need to find the atomic and mass numbers of X: Atomic number (protons) = 42 (from \(^{96}_{42} Mo\)) + 1 (from \(^{2}_{1}D\ or\ ^{2}_{1}H\)) = 43 Mass number (protons + neutrons) = 96 (from \(^{96}_{42} Mo\)) + 2 (from \(^{2}_{1}D\ or\ ^{2}_{1}H\)) = 98 The nuclear equation for this process is: \(^{96}_{42} Mo + ^{2}_{1}D \rightarrow ^{98}_{43}X\) Step 5: Identify the new element

Step 5: Identify the new element

The balanced nuclear equation gives us a new element with atomic number 43, and mass number 98. By looking at a periodic table, we can find that element 43 is Technetium (Tc). So, the nuclear equation representing this process is: \(^{96}_{42} Mo + ^{2}_{1}D \rightarrow ^{98}_{43}Tc\) The element produced by Ernest Lawrence when he bombarded a molybdenum target with deuterium ions, for the first time, is Technetium.

Key Concepts

Cyclotron

A cyclotron is an apparatus invented by physicist Ernest Lawrence in the 1930s in Berkeley, California. Its main purpose is to accelerate charged particles, such as ions, to high speeds. This acceleration is achieved using a combination of a magnetic field and an alternating electric field.
When particles are placed in the cyclotron, they are subjected to magnetic forces which cause them to spiral outward in a path. As they traverse this spiral, they are accelerated by the electric field, gaining energy with each turn. The increased energy allows them to reach speeds necessary to overcome repulsive forces between atomic nuclei, making cyclotrons particularly useful in conducting nuclear reactions.

• Cyclotrons enable the production of new elements or isotopes, which are crucial for scientific research and medical applications.
• They have been pivotal in various discoveries, one of which was the production of technetium, the first artificial element.

Ernest Lawrence's cyclotron marked a significant advancement in nuclear chemistry, proving instrumental in synthesizing elements not found naturally on Earth.

Nuclear Reaction

A nuclear reaction involves changes in an atom's nucleus, resulting in the transformation of elements. Unlike chemical reactions that involve electrons, nuclear reactions focus on protons and neutrons within the nucleus.
In the context of Lawrence's experiment using a cyclotron, the process began by bombarding a molybdenum target (containing Mo-96 isotopes) with deuterium ions. A deuterium ion (or heavy hydrogen) consists of one proton and one neutron. By projecting this ion towards molybdenum atoms, the reaction induced a change in the nucleus.

• The resulting nuclear reaction formula can be represented as:
  \[^{96}_{42} Mo + ^{2}_{1}D \rightarrow ^{98}_{43}Tc\]
• This equation demonstrates the creation of a new element: technetium, with an atomic number of 43 and mass number 98.

Nuclear reactions like this are critical to understanding the creation and transformation of elements, which is a cornerstone of nuclear chemistry.

Element Synthesis

Element synthesis refers to the process of creating new chemical elements. This can be done either artificially in laboratories or naturally, such as in stars.
In laboratories, element synthesis is achieved by using particle accelerators, like cyclotrons, to initiate nuclear reactions. By bombarding nuclei with other particles, it's possible to create new elements that do not exist naturally on earth, known as "synthetic elements."

• The synthesis of technetium is an example where Ernest Lawrence successfully created an element by bombarding molybdenum with deuterium ions, advancing both scientific knowledge and experimental techniques.
• These synthetic elements are essential in expanding the periodic table, providing chemists with a deeper understanding of atomic structure and nuclear forces.

Through element synthesis, scientists can study the properties and potential applications of new elements, contributing significantly to fields such as medicine, industry, and energy.

Technetium

Technetium holds the distinction of being the first element to be artificially produced. With the atomic number 43, it fills a unique spot between molybdenum and ruthenium on the periodic table.
This element was synthesized by bombarding molybdenum with deuterium, resulting in technetium with a mass number of 98. Technetium is not naturally occurring on Earth, making its discovery pivotal for the development of nuclear chemistry.

• Technetium isotopes, especially Tc-99m, are widely used in medical imaging, such as in certain types of nuclear medicine scans.
• Due to its radioactive nature, technetium must be handled with care, but its usefulness in diagnostic processes cannot be overstated.

The discovery and production of technetium underscored the capability of scientists to create useful elements beyond what is naturally available, demonstrating the power and potential of nuclear chemistry advancements.