Mention the range of mass number for which the Binding energy curve is almost horizontal.

Explanation

To solve the question regarding the range of mass number for which the binding energy curve is almost horizontal, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Binding Energy Curve**: The binding energy curve represents the binding energy per nucleon as a function of the mass number (A). It shows how stable a nucleus is based on its mass number.

2. **Identifying the Trend**: As we plot the binding energy per nucleon against the mass number, we observe that the curve rises sharply for small mass numbers (like hydrogen and helium) and reaches a peak around iron (Fe), which has the highest binding energy per nucleon.

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