The symbol for a radioactive nuclide is ${ }_{56}^{131} Ba$. Which statement is correct?
A. The atomic number of the radioactive nuclide is 75.
B. The mass number of the radioactive nuclide is 131.
C. The number of neutrons that are present in the nucleus of each atom is 56.
D. The number of protons that are present in the nucleus of each atom is 131.
Answer (2)
The atomic number (56) represents the number of protons.
The mass number (131) represents the total number of protons and neutrons.
Calculate the number of neutrons: 131 − 56 = 75 .
The correct statement is that the mass number of the radioactive nuclide is 131 .
Explanation
Problem Analysis We are given the radioactive nuclide 56 131 B a . We need to determine which of the given statements is correct. Let's analyze the notation and the statements.
Understanding the Notation The notation 56 131 B a tells us two important numbers:
The subscript (56) is the atomic number, which represents the number of protons in the nucleus.
The superscript (131) is the mass number, which represents the total number of protons and neutrons in the nucleus.
Evaluating the Statements Now, let's examine each statement:
"The atomic number of the radioactive nuclide is 75." This is incorrect because the atomic number is 56.
"The mass number of the radioactive nuclide is 131." This is correct because the mass number is indeed 131.
"The number of neutrons that are present in the nucleus of each atom is 56." To find the number of neutrons, we subtract the atomic number (number of protons) from the mass number (number of protons + neutrons): 131 − 56 = 75 . So, this statement is incorrect.
"The number of protons that are present in the nucleus of each atom is 131." This is incorrect because the number of protons is the atomic number, which is 56.
Conclusion Therefore, the correct statement is: "The mass number of the radioactive nuclide is 131."
Examples
Understanding the structure of atoms, like the radioactive nuclide 56 131 B a , is crucial in various fields. For example, in nuclear medicine, radioactive isotopes are used for diagnostic imaging and cancer treatment. Knowing the atomic number, mass number, and number of neutrons helps scientists predict the stability and decay pathways of these isotopes, ensuring their safe and effective use in medical applications. In environmental science, understanding radioactive decay is essential for monitoring and managing radioactive waste. The mass number helps determine the half-life and decay products of radioactive materials, which is vital for assessing their long-term impact on the environment.
The correct statement regarding the radioactive nuclide 56 131 B a is that the mass number is 131. This is derived from the notation, where 56 is the atomic number indicating the number of protons. The other statements regarding atomic and neutron counts are incorrect.
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