To determine the number of neutrons in a single [tex]\(Fe^{2+}\)[/tex] atom with a mass number of 56, we need to understand the relationship between the mass number, atomic number, and the number of neutrons.
The mass number (A) of an atom is the sum of the number of protons (atomic number, Z) and the number of neutrons (N) in the nucleus:
[tex]\[ \text{Mass number} (A) = \text{Number of protons} + \text{Number of neutrons} \][/tex]
[tex]\[ A = Z + N \][/tex]
For iron ([tex]\(Fe\)[/tex]), the atomic number (Z) is 26. This means that a neutral iron atom has 26 protons in its nucleus.
Given:
- Mass number ([tex]\(A\)[/tex]) = 56
- Atomic number ([tex]\(Z\)[/tex]) = 26
We need to find the number of neutrons (N):
[tex]\[ N = A - Z \][/tex]
Substitute the given values into the equation:
[tex]\[ N = 56 - 26 \][/tex]
[tex]\[ N = 30 \][/tex]
Thus, the number of neutrons in a single [tex]\(Fe^{2+}\)[/tex] atom is 30.
Therefore, the correct answer is:
30
