Question

In \(2006,\) Alexander Litvinenko, a vocal critic of the Putin government in Russia, was poisoned in London with a lethal dose of polonium- 210 injected by Russian agents. Polonium- 210 is synthesized by the uptake of a neutron by bismuth-209. Write a balanced nuclear equation to represent this process.

Short answer

The balanced nuclear equation is: \[ _{83}^{209}\text{Bi} + _{0}^{1}\text{n} \to _{84}^{210}\text{Po} + _{-1}^{0}\text{e} \]

Step-by-step solution

Identify the Initial Reactants

We start with bismuth-209 and a neutron as the reactants, as given in the problem statement. The isotope of bismuth is represented as \( _{83}^{209}\text{Bi} \), and a neutron is represented as \( _{0}^{1}\text{n} \).

Write the Nuclear Equation

In a nuclear equation, the sum of the atomic numbers (the subscript) and the sum of the mass numbers (the superscript) are conserved on both sides of the reaction. Start writing the equation:\[ _{83}^{209}\text{Bi} + _{0}^{1}\text{n} \to ... \]

Determine the Product Isotopes

The absorption of a neutron by bismuth-209 will lead to the formation of polonium-210. Polonium-210 is represented by \( _{84}^{210}\text{Po} \). Therefore, the equation becomes:\[ _{83}^{209}\text{Bi} + _{0}^{1}\text{n} \to _{84}^{210}\text{Po} \]

Check for Conservation of Mass and Atomic Number

Ensure that the total atomic numbers and mass numbers on both sides of the equation are equal. On the left side, the total atomic number is 83 (bismuth) + 0 (neutron) = 83, and the total mass number is 209 + 1 = 210. On the right side, for polonium, the atomic number is 84, and the mass number is 210. The atomic numbers are not conserved, indicating the need for another emitted particle.

Balance the Equation by Including an Emitted Particle

To balance the atomic numbers, include an emitted particle. The missing particle is likely a beta particle (electron), represented as \( _{-1}^{0}\beta \). The full nuclear equation now reads:\[ _{83}^{209}\text{Bi} + _{0}^{1}\text{n} \to _{84}^{210}\text{Po} + _{-1}^{0}\text{e} \]

Confirm the Equation Balancing

Verify the conservation of atomic numbers: 83 (bismith) + 0 (neutron) equals 84 (polonium) + (-1) (electron). Similarly, the mass numbers on the left (209 + 1 = 210) match perfectly with those on the right (210).

Key concepts

Polonium-210

Polonium-210 is a highly radioactive isotope of the element polonium. It belongs to the group of actinide-related elements in the periodic table. Polonium itself is a relatively rare element and was discovered by Marie Curie in 1898. The specific isotope Polonium-210 is denoted by \( _{84}^{210} \text{Po} \), where the subscript 84 represents its atomic number, indicating that it has 84 protons, and the superscript 210 denotes its mass number, which includes protons and neutrons.

The importance of Polonium-210 lies in its use in various fields, such as neutron sources and sometimes as a heat source in space exploration. However, it is most infamously known for its extremely potent nature as a poison, as evidenced in historical events like the poisoning of Alexander Litvinenko. A tiny amount, even less than a microgram, is enough to exert lethal effects if ingested or injected.

This isotope undergoes alpha decay, which is a process where it releases an alpha particle, transforming into a different element. Polonium-210 decays into lead-206, releasing energy in the form of radiation. As a result, handling this isotope requires expertise and strict safety measures to avoid harmful exposure.

Neutron Absorption

Neutron absorption is a critical process in nuclear reactions where a neutron is incorporated into the nucleus of an atom. This process can lead to a change in the atomic nucleus, resulting in the formation of new isotopes or elements. In the example of Polonium-210 formation, a neutron is absorbed by Bismuth-209, leading to changes in its composition.

The formula for such a reaction is usually written in a way that conserves both mass and atomic numbers:

• The starting element (e.g. Bismuth-209) and the neutron combine to form a heavier element (Polonium-210 in this case).
• The reaction is often accompanied by the emission of particles such as electrons or gamma rays due to energy balancing requirements.

Neutron absorption is not only important in natural processes but also has significant practical applications. For example, in nuclear reactors, controlled neutron absorption is key to sustaining and regulating the fission chain reaction. Additionally, neutron absorption is used in neutron activation analysis, a technique to determine elemental composition in samples.

Radioactive Decay

Radioactive decay is a natural and spontaneous process where unstable atomic nuclei lose energy by emitting radiation. This process allows nuclei to achieve a more stable energy state. There are several types of radioactive decay, with alpha, beta, and gamma decay being the most common.

In connection with Polonium-210, this isotope undergoes alpha decay. When an atom undergoes alpha decay, it emits an alpha particle, which consists of two protons and two neutrons. This is essentially a helium nucleus. For Polonium-210, the alpha decay transforms it into lead-206 by reducing its atomic number by two (from 84 to 82) and its mass number by four (from 210 to 206).

• This type of decay is often accompanied by the release of energy in the form of radiation.
• The decay process is random, but each radionuclide has a characteristic half-life, which is the time taken for half of the radioactive isotopes in a sample to decay.

Polonium-210 has a half-life of around 138 days, which makes it potent and hazardous over a relatively foreseeable period. Understanding radioactive decay is crucial not just in nuclear chemistry, but also in fields like archaeology (radiocarbon dating), medicine (radiotherapy), and energy generation.