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In nuclear reactions, an alpha particle is essentially a helium nucleus, consisting of two protons and two neutrons. This gives it a total mass number of 4 and an atomic number of 2. When a nucleus emits an alpha particle, the atomic number of the nucleus decreases by 2, and the mass number decreases by 4. This is because the emitted alpha particle takes away both mass and charge from the original nucleus, effectively transforming the nucleus into a different chemical element.

• Mass Number Change: -4
• Atomic Number Change: -2

For example, when curium-242 absorbs an alpha particle and emits two neutrons, its mass number should be adjusted by adding the alpha particle’s mass (+4), then subtracting the mass of the two emitted neutrons (-2), leading to a mass number of 244. The atomic number, after adding the alpha particle's contribution, should increase by 2 from 96 to 98.

Neutron absorption is a crucial aspect of nuclear reactions where a neutron is captured by a nucleus. This process doesn’t change the electric charge of the nucleus since neutrons are neutral, but it does increase the nucleus’s mass number by one.

• Mass Number Change: +1
• Atomic Number Change: 0

An example of neutron absorption can be seen in the transformation of nitrogen-14 to carbon-14. Here, nitrogen absorbs a neutron and emits a proton, causing only the mass to remain the same because one particle adds and one subtracts atomic mass but the breakdown affects the atomic structure turning nitrogen into carbon.

The atomic number of an element is defined by the number of protons in the nucleus. Any change in this number results in the formation of a new element. Nuclear reactions often involve the emission or absorption of particles that change an element's atomic number.

• Alpha Emission: Atomic Number -2
• Neutron Absorption: Atomic Number unchanged initially, but may result in changes due to subsequent reactions.
• Proton Emission (as seen in neutron-proton transformations): Atomic Number -1

These changes are fundamental in nuclear chemistry, as they determine the type of reactions and the nature of the elements formed. For instance, the absorption of an alpha particle adds 2 to the atomic number, while proton emission will reduce it by 1.

The mass number of a nucleus is the total of its protons and neutrons. During nuclear reactions, especially those involving emission or absorption of particles, precise calculations are crucial to know the resultant element's identity.

• Alpha Particle Impact: Adds 4 to mass number, but adjustments are made based on additional particle emissions.
• Neutron Absorption: Each neutron absorbed adds 1 to the mass number.
• Particle Emission: Adjust mass calculation by subtracting the mass of emitted particles.

These calculations help chemists predict the results of nuclear reactions. For instance, checking the correctness of a nuclear product, as questioned in typical textbook exercises, involves careful mass number calculations to ensure identities and quantities match theoretical expectations, as seen in the example with curium-242 transforming post alpha particle absorption.