Alpha decay is a type of radioactive decay where an unstable nucleus emits an alpha particle, which is composed of 2 protons and 2 neutrons. This means that the atomic number of the alpha particle is 2, corresponding to helium, and its mass number is 4, as it is the sum of the protons and neutrons. Therefore, an alpha particle can be represented as either He4 or the alpha symbol (α).

Alpha decay typically occurs in heavy nuclei that have an excess of protons and neutrons. The process results in the formation of a stable helium atom, specifically the helium-4 isotope. When balancing nuclear reactions, it is crucial to ensure that both the atomic number (number of protons) and the mass number (total number of protons and neutrons) are equal on both sides of the equation.

For example, consider the decay of platinum-171 (Pt₇₈) emitting an alpha particle. The mass number on the reactant side is 171, and the alpha particle contributes a mass number of 4. To maintain balance, the product side must also total 171. Thus, the remaining mass number must be 167, leading to the formation of osmium-167 (Os₇₆). The atomic number on the reactant side is 78, and since the alpha particle contributes 2 protons, the remaining number of protons must be 76, which corresponds to osmium on the periodic table.

In summary, the alpha decay of platinum-171 can be expressed as:

Pt₇₈¹⁷¹ → Os₇₆¹⁶⁷ + α

It is essential to ensure that both the mass number and the atomic number are conserved during nuclear reactions, confirming that the total counts are equal on both sides of the equation. This principle is fundamental in understanding nuclear chemistry and the behavior of radioactive isotopes.

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