the mass number of fe²⁺ is 56. how many neutrons are there in a single fe²⁺ atom?\no 28\no 30\no 56\no 58

Explanation:

Step1: Recall atomic number of Fe

The atomic number of iron (Fe) is 26. It represents the number of protons.

Step2: Use mass - number formula

The mass number (A) is the sum of protons (p) and neutrons (n), i.e., $A=p + n$. We know $A = 56$ and $p=26$. So, $n=A - p$.

Step3: Calculate number of neutrons

Substitute the values: $n=56 - 26=30$.

Answer:

30