Alpha Decay: Videos & Practice Problems

Alpha decay is a type of radioactive decay where an unstable nucleus emits an alpha particle, which consists of 2 protons and 2 neutrons. This process results in a decrease in the atomic mass of the original element by 4 units, as the atomic mass is calculated by the sum of protons and neutrons. The alpha particle can be represented as:

$$\frac{4}{2} \text{He}$$

Here, the alpha particle is equivalent to the element Helium, which has the same atomic mass of 4 and an atomic number of 2.

To illustrate alpha decay, consider the isotope Polonium-210 (represented as Po), which has an atomic mass of 210 and an atomic number of 84. During alpha decay, Polonium-210 emits an alpha particle:

$$\text{Po}_{84}^{210} \rightarrow \text{He}_{2}^{4} + \text{Pb}_{82}^{206}$$

In this reaction, the total atomic mass must be conserved. The original atomic mass of 210 is balanced by the sum of the emitted alpha particle (4) and the new element, Lead-206 (206). Therefore, the new element formed after the decay is Lead-206, which has an atomic number of 82. This ensures that the atomic numbers also balance, as 84 (from Polonium) equals 2 (from Helium) plus 82 (from Lead).

In summary, alpha decay transforms Polonium-210 into Lead-206 while emitting an alpha particle, Helium, as a byproduct. It is crucial to ensure that both atomic mass and atomic number are balanced in nuclear reactions, similar to balancing in chemical reactions.

Alpha particles are the largest type of radioactive particles, surpassing both beta and gamma particles in size. Due to their significant mass, alpha particles possess the highest ionizing power, making them particularly damaging to biological cells. If an alpha particle were to enter the body, it could cause severe internal damage, leading to a very low chance of survival for the exposed individual. This high ionizing power means that alpha particles can effectively shred biological tissues, resulting in extensive irradiation of cells.

Despite their destructive potential, alpha particles have the lowest penetrating power among radioactive particles. They are unable to penetrate the skin and are effectively blocked by clothing and even the air surrounding us. This characteristic makes it challenging for alpha particles to enter the body under normal circumstances. Potential exposure could occur in specific environments, such as nuclear facilities, where contaminated water or food might lead to ingestion of alpha-emitting materials. However, such scenarios are relatively rare, and the natural barriers provided by our skin and clothing offer substantial protection against alpha radiation.

In nuclear chemistry, understanding alpha emissions and their corresponding balanced equations is crucial. An alpha emission, or decay, involves the release of an alpha particle, which is essentially a helium nucleus (He or ⁴He). To illustrate this, consider the decay of Curium-248. The atomic number of Curium (Cm) is 96, and its atomic mass is 248. When Curium-248 undergoes alpha decay, it emits an alpha particle, resulting in the formation of Plutonium-244. The balanced nuclear equation can be expressed as:

Curium-248 Decay:

^{248}_{96}Cm \rightarrow ^{244}_{94}Pu + ^{4}_{2}He

Here, the atomic mass on the left (248) equals the sum of the atomic masses on the right (244 + 4), and the atomic numbers also balance (96 = 94 + 2).

Next, consider Bismuth-207, which has an atomic number of 83. When it undergoes alpha decay, it also emits an alpha particle, resulting in Thallium-203. The balanced equation for this decay is:

Bismuth-207 Decay:

^{207}_{83}Bi \rightarrow ^{203}_{81}Tl + ^{4}_{2}He

Again, the atomic masses and numbers are balanced, confirming the accuracy of the equation.

In contrast, alpha absorption or capture involves an alpha particle being a reactant rather than a product. For example, when Calcium-40 captures an alpha particle, the equation is set up as follows:

Calcium-40 Capture:

^{40}_{20}Ca + ^{4}_{2}He \rightarrow ^{44}_{22}Ti

In this case, the atomic mass increases from 40 to 44, and the atomic number increases from 20 to 22, leading to the formation of Titanium-44. This process highlights the importance of referencing the periodic table to identify the resulting elements based on their atomic numbers.