How many protons, neutrons, and electrons are in this ion?
${ }_{31}^{71} Ga^{3+}$
A. $31 p^+, 40 n^0, 28 e^-$
B. $31 p^+, 40 n^0, 31 e^-$
C. $31 p^+, 71 n^0, 31 e^-$
D. $40 p^+, 31 n^0, 40 e^-$
Answer (2)
The number of protons equals the atomic number: 31.
The number of neutrons equals the mass number minus the atomic number: 71 − 31 = 40 .
The number of electrons equals the number of protons minus the charge: 31 − 3 = 28 .
Therefore, the ion has 31 p + , 40 n 0 , 28 e − .
Explanation
Understanding the Ion Notation We are asked to determine the number of protons, neutrons, and electrons in the given ion, 31 71 G a 3 + . Let's break down what each part of this notation means.
Determining the Number of Protons The subscript 31 represents the atomic number of Gallium (Ga). The atomic number is the number of protons in the nucleus of an atom. Therefore, the number of protons in this ion is 31.
Determining the Number of Neutrons The superscript 71 represents the mass number of the ion. The mass number is the total number of protons and neutrons in the nucleus. To find the number of neutrons, we subtract the number of protons (atomic number) from the mass number: 71 − 31 = 40 . So, there are 40 neutrons in this ion.
Determining the Number of Electrons The 3 + superscript on the right side of the element symbol indicates the charge of the ion. A 3 + charge means that the ion has lost 3 electrons. In a neutral atom, the number of electrons is equal to the number of protons. Since Gallium has 31 protons, a neutral Gallium atom would have 31 electrons. However, this ion has a 3 + charge, so it has 31 − 3 = 28 electrons.
Final Answer Therefore, the 31 71 G a 3 + ion has 31 protons, 40 neutrons, and 28 electrons.
Examples
Understanding the composition of ions is crucial in various fields. For example, in medicine, radioactive isotopes like Gallium-67 ( 67 Ga) are used in imaging techniques to detect tumors and inflammation. Knowing the number of protons, neutrons, and electrons helps scientists predict the behavior and properties of these isotopes, ensuring accurate diagnosis and treatment. Similarly, in materials science, understanding the ionic composition of materials helps in designing new compounds with specific electrical and magnetic properties.
The 31 71 G a 3 + ion has 31 protons, 40 neutrons, and 28 electrons. Therefore, the correct answer is option A: 31 p + , 40 n 0 , 28 e − .
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