A represents atomic mass and 2 represents an atomic number, which of the following describes an atom after a proton is emitted?
A.
A-1,2-1
B.
A-1,2+1
C.
A,2-1
D.
A+1,2-1
The Correct answer and Explanation is:
The correct answer is A. A-1,2-1.
Explanation:
To understand what happens to an atom when a proton is emitted, we first need to review some fundamental concepts about atomic structure and radioactive decay.
- Atomic Structure Basics:
- Atomic Mass (A): This is the total number of protons and neutrons in the nucleus of an atom.
- Atomic Number (Z): This is the number of protons in the nucleus, which determines the element’s identity and its position in the periodic table.
- Proton Emission:
- When a proton is emitted from an atom, it essentially undergoes a type of radioactive decay called beta-plus decay. This results in the transformation of a proton into a neutron, with the emission of a positron and a neutrino.
- Effects of Proton Emission:
- Change in Atomic Number (Z): The emission of a proton reduces the atomic number of the atom by 1. This is because a proton, which is positively charged, is lost from the nucleus.
- Change in Atomic Mass (A): Since the emission of a proton converts it into a neutron, the total count of nucleons (protons and neutrons) decreases by 1. Therefore, the atomic mass (A) also decreases by 1.
Let’s use these principles to analyze each option:
- Option A: A-1,2-1
- A-1: This indicates that the atomic mass has decreased by 1, which is correct since one proton is lost.
- 2-1: This indicates that the atomic number has decreased by 1, which is correct because the loss of one proton results in a lower atomic number.
- Option B: A-1,2+1
- A-1: Correctly shows the atomic mass decrease, but
- 2+1: Incorrectly shows an increase in the atomic number. The atomic number should decrease, not increase.
- Option C: A,2-1
- A: The atomic mass should decrease by 1, not stay the same.
- 2-1: Correctly shows the atomic number decrease, but the atomic mass is incorrect.
- Option D: A+1,2-1
- A+1: Incorrectly shows an increase in atomic mass. The atomic mass should decrease by 1.
- 2-1: Correctly shows the decrease in atomic number, but the atomic mass is incorrect.
In summary, after a proton is emitted, the atomic mass of the atom decreases by 1 (from A to A-1), and the atomic number decreases by 1 (from Z to Z-1). Therefore, the correct description of the atom after a proton is emitted is A-1,2-1.