Which of the following statements is not true?

The correct answer is Option (1) → The constancy of the binding energy per nucleon for \( 30\lt A\lt 170 \) is due to the fact that nuclear forces are long range forces.

The key properties of nuclear forces are that they are very strong and short range; each nucleon interacts only with its nearest neighbours.

Option (1) The constancy of the binding energy per nucleon for \( 30\lt A\lt 170 \) is due to the fact that nuclear forces are long range forces. — Incorrect. The constancy is due to the short range of nuclear forces: a nucleon feels only its nearest neighbours.

Option (2) The saturation property of the nuclear forces is due to the fact that nuclear forces are short range forces. — Correct. A nucleon binds with only a limited number of neighbours.

Option (3) Energy is released in nuclear fission reaction because the binding energy per nucleon of the heavier initial nucleus is lower than that of its intermediate mass fragments. — Correct. The fragments (A about 120) are more tightly bound than the nucleus with A about 240.

Option (4) Energy is released in nuclear fusion reaction because the larger nucleus formed after the reaction is more tightly bound than the two initial lighter nuclei. — Correct. The fused nucleus has a higher binding energy per nucleon.

NCERT (2026-27):
Nuclear Binding Energy – “… (ii) The constancy of the binding energy in the range 30 < A < 170 is a consequence of the fact that the nuclear force is short-ranged.”

Nuclear Binding Energy – “… The property that a given nucleon influences only nucleons close to it is also referred to as saturation property of the nuclear force.”