To determine the number of neutrons in a single [tex]\( Fe^{2+} \)[/tex] atom with a mass number of 56, we can follow these steps:
1. Identify the Atomic Number: Iron (Fe) has an atomic number of 26. The atomic number represents the number of protons in an atom.
2. Understanding Mass Number: The mass number is the sum of protons and neutrons in the nucleus of an atom. For [tex]\( Fe \)[/tex], the mass number is given as 56.
3. Formula for Neutrons: The number of neutrons can be calculated by subtracting the number of protons from the mass number. The formula is:
[tex]\[
\text{Number of neutrons} = \text{Mass number} - \text{Number of protons}
\][/tex]
4. Apply the Values:
[tex]\[
\text{Number of neutrons} = 56 - 26 = 30
\][/tex]
Therefore, the number of neutrons in a single [tex]\( Fe^{2+} \)[/tex] atom with a mass number of 56 is 30.
Among the given choices, the correct answer is:
[tex]\[
30
\][/tex]
