The energy required to separate the nucleus in an atom completely is known as

Step 1: Analyze the question The question asks for the name of the energy needed to completely separate a nucleus into its individual particles (protons and neutrons, collectively called nucleons).

Step 2: Explain the concept Protons and neutrons are held together in the nucleus by the strong nuclear force. To pull them apart completely, you must supply energy equal to the energy that holds them together. This is called the nuclear binding energy.

It is linked to the mass defect (Δm), which is the difference between the mass of the separate nucleons and the actual mass of the nucleus:

Δm = (Z·mₚ + N·mₙ) − m(nucleus)

The binding energy comes from Einstein's mass-energy relation:

E = Δm · c²

Step 3: Check each option

• A. Mass defect of the atom: This is a mass, not an energy. It is related to the binding energy, but it is not the energy itself. ✗
• B. Electron binding energy: This is the energy needed to remove electrons from the atom (related to ionization energy). It is not about separating the nucleus. ✗
• C. Excitation energy: This is the energy needed to raise an electron or nucleus to a higher energy level. It does not separate anything completely. ✗
• D. Nuclear binding energy: This is the energy required to break the nucleus into its separate nucleons. ✓

Step 4: Answer The correct option is D. nuclear binding energy.

Tip: Remember the pairing: mass defect is the "missing mass" and binding energy is that missing mass converted to energy (E = Δmc²). If the question says "energy" and "nucleus," think nuclear binding energy. If it says "mass difference," think mass defect.