If A represents atomic mass and Z represents atomic number, which of the following describes an atom after a proton is emitted from its nucleus?

Rationale

A-1, Z-1

When a proton is emitted from an atomic nucleus, the atomic mass (A) decreases by 1 since one proton is lost, and the atomic number (Z) also decreases by 1 because the number of protons defining the element's identity is reduced. This results in both A and Z decreasing by one unit.

A (A+1, Z-1) YOUR ANSWER

This option incorrectly suggests that the atomic mass increases by one unit while the atomic number decreases by one. Emission of a proton results in a loss of mass and a decrease in atomic number, not an increase in mass.

B (A-1, Z+1) YOUR ANSWER

This choice states that the atomic mass decreases by one, which is correct; however, it erroneously claims that the atomic number increases by one. Emitting a proton reduces the atomic number by one, not increases it.

C (A+1, Z+1) YOUR ANSWER

This incorrect option suggests that both the atomic mass and atomic number increase by one. In reality, the emission of a proton leads to a decrease in both values, directly contradicting the fundamental behavior of atomic nuclei during proton emission.

D (A-1, Z-1) CORRECT

This choice accurately reflects the changes that occur during the emission of a proton: the atomic mass decreases by 1 due to the loss of a proton, and the atomic number decreases by 1 as well, resulting in a different element.

Conclusion

The correct understanding of proton emission from an atomic nucleus indicates that both the atomic mass and atomic number decrease by one. This fundamental process alters the identity of the atom, transforming it into a different element. By recognizing that A decreases by one and Z decreases by one, we can accurately describe the transformation that occurs during this nuclear reaction.

If A represents atomic mass and Z represents atomic number, which of the following describes an atom after a proton is emitted from its nucleus?

A-1, Z-1

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