Problem 91 - Chemistry The Science in Context

Question

Synthesis of a New Element In 2006 an international team of scientists confirmed the synthesis of a total of three atoms of \(_{118}^{294} \mathrm{Og}\) in experiments run in 2002 and \(2005 .\) They had bombarded a \(^{249} \mathrm{Cf}\) target with \(^{48} \mathrm{Ca}\) nuclei. a. Write a balanced nuclear equation describing the synthesis of \(_{118}^{294} \mathrm{Og}\) b. The synthesized isotope of Og undergoes \(\alpha\) decay \(\left(t_{1 / 2}=0.9 \mathrm{ms}\right) .\) What nuclide is produced by the decay process? c. The nuclide produced in part (b) also undergoes \(\alpha\) decay \(\left(t_{1 / 2}=10 \mathrm{ms}\right) .\) What nuclide is produced by this decay process? d. The nuclide produced in part (c) also undergoes \(\alpha\) decay \(\left(t_{1 / 2}=0.16 \mathrm{s}\right) .\) What nuclide is produced by this decay process? e. If you had to select an element that occurs in nature and that has physical and chemical properties similar to Og, which element would it be?

Step-by-Step Solution

Answer

Answer: Radon (Rn) would be the element chosen as having physical and chemical properties similar to Oganesson (Og). The products of the subsequent α decays of oganesson are as follows: In the first decay, Livermorium (_{116}^{290}Lv) is produced. In the second decay, Flerovium (_{114}^{286}Fl) is produced. In the third decay, Copernicium (_{112}^{282}Cn) is produced.

Step 1: List the reactants and products

For this reaction, the reactants are given as \(^{249}\mathrm{Cf}\) and \(^{48}\mathrm{Ca}\), and the product is \(_{118}^{294}\mathrm{Og}\).

Step 2: Balance the equation

We can find the missing product, which is a neutron, by balancing the atomic and mass numbers on both sides of the equation. We have: \(^{249}\mathrm{Cf}\ +\ ^{48}\mathrm{Ca}\ \to\ _{118}^{294}\mathrm{Og}\ +\ ^{1}_{0}\mathrm{n}\) b. The synthesized isotope of Og undergoes α decay \((t_{1/2}=0.9\ \mathrm{ms})\). What nuclide is produced by the decay process?

Step 3: Understand alpha decay

In alpha decay, a nucleus emits an alpha particle composing of 2 protons and 2 neutrons, represented as \(^{4}_{2}\mathrm{He}\) or \(\alpha\).

Step 4: Find the product of the first α decay

Since \(_{118}^{294}\mathrm{Og}\) undergoes α decay, we write the equation and find the missing product: \(_{118}^{294}\mathrm{Og}\ \to\ _{Z}^{A}\mathrm{X}\ +\ ^{4}_{2}\mathrm{He}\) We have \(A = 294 - 4 = 290\) and \(Z = 118 - 2 = 116\). Therefore, the nuclide produced by the first α decay is \(_{116}^{290}\mathrm{Lv}\). c. The nuclide produced in part (b) also undergoes α decay \((t_{1/2}=10\ \mathrm{ms})\). What nuclide is produced by this decay process?

Step 5: Find the product of the second α decay

Since \(_{116}^{290}\mathrm{Lv}\) also undergoes α decay, we write down the equation and find the missing product: \(_{116}^{290}\mathrm{Lv}\ \to\ _{Z}^{A}\mathrm{X}\ +\ ^{4}_{2}\mathrm{He}\) We have \(A = 290 - 4 = 286\) and \(Z = 116 - 2 = 114\). Therefore, the nuclide produced by the second α decay is \(_{114}^{286}\mathrm{Fl}\). d. The nuclide produced in part (c) also undergoes α decay \((t_{1/2}=0.16\ \mathrm{s})\). What nuclide is produced by this decay process?

Step 6: Find the product of the third α decay

Since \(_{114}^{286}\mathrm{Fl}\) also undergoes α decay, we write down the equation and find the missing product: \(_{114}^{286}\mathrm{Fl}\ \to\ _{Z}^{A}\mathrm{X}\ +\ ^{4}_{2}\mathrm{He}\) We have \(A = 286 - 4 = 282\) and \(Z = 114 - 2 = 112\). Therefore, the nuclide produced by the third α decay is \(_{112}^{282}\mathrm{Cn}\). e. If you had to select an element that occurs in nature and that has physical and chemical properties similar to Og, which element would it be?

Step 7: Finding an element similar to Og

The physical and chemical properties of elements are largely determined by their position in the periodic table, particularly their group. Og is a member of Group 18, also known as the Noble Gases. Therefore, an element that occurs naturally and has similar properties to Og would be another noble gas. The choices are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), or radon (Rn). Since Og is the heaviest noble gas, we can select Radon (Rn), the heaviest naturally-occurring noble gas, as the element with properties most similar to Og.

Key Concepts

Nuclear Equations

Nuclear equations help us visualize and understand changes that occur at the nuclear level during nuclear reactions. When scientists succeed in synthesizing a new element, such as Oganesson (Og), understanding these equations becomes crucial. They show how protons, neutrons, and, in some cases, electrons are rearranged. For the synthesis of \( _{118}^{294}\mathrm{Og}\), the nuclear equation given was:

• Reactants: \(^{249}\mathrm{Cf}\) and \(^{48}\mathrm{Ca}\)
• Product: \( _{118}^{294}\mathrm{Og}\) and a neutron \( ^{1}_{0}\mathrm{n}\)

This equation is balanced because:

• Atomic numbers add up: \( 98 + 20 = 118\)
• Mass numbers add up: \(249 + 48 = 294 + 1\)

Balancing nuclear equations requires us to ensure that the sum of mass numbers and the atomic numbers are the same on both sides of the equation.

Alpha Decay

Alpha decay is a type of radioactive decay where an unstable atom emits an alpha particle, consisting of 2 protons and 2 neutrons. This particle is essentially a helium ion \(^{4}_{2}\mathrm{He}\). When \( _{118}^{294}\mathrm{Og}\) undergoes alpha decay, it results in the formation of a new element:

• Decrease in atomic number by 2: \(118 - 2 = 116\)
• Decrease in mass number by 4: \(294 - 4 = 290\)

Hence, the nuclide becomes \( _{116}^{290}\mathrm{Lv}\). Understanding this allows us to track how elements transform over time, decaying into different nuclides through the emission of particles like alpha particles. This process is crucial in nuclear chemistry and understanding radioactivity.

Periodic Table

The periodic table is a systematic way of organizing elements based on their atomic number, electronic configuration, and recurring chemical properties. Oganesson (Og) is positioned in the periodic table as element 118, making it a noble gas. Its placement in Group 18 suggests similarities in physical and chemical properties with other noble gases. Each group in the periodic table shares similar traits, primarily due to the arrangement of electrons. For Og, being at the bottom of the noble gas group, it shares properties like being inert and having complete electron shells.

Noble Gases

Noble gases are elements found in Group 18 of the periodic table, known for their stability and lack of reactivity due to having full outer electron shells. These gases include helium, neon, argon, krypton, xenon, and radon. They are used in various applications:

• Neon for lighting
• Helium in balloons
• Xenon in headlights

Oganesson, like other noble gases, is likely very stable, though as a synthetic element, much about its properties is yet to be confirmed. Among naturally occurring noble gases, radon shares the most similarities with oganesson, bottoming the group alongside it as the heaviest elements. Due to their non-reactive nature, noble gases have unique applications in creating safe environments to protect reactive substances.