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WAEC Physics 2017 Paper

Question : 48

Total: 50

Solution:

Concept:

Ionisation energy is the energy required to remove an electron from the ground state to infinity, where the energy at infinity is zero.

Explanation:

The ground state is the lowest energy level, which is

E_0 = -10.4\,\text{eV}

At infinity, the energy is

E_{\infty} = 0\,\text{eV}

Ionisation energy is the difference:

E_{\infty} - E_0 = 0 - (-10.4\,\text{eV}) = +10.4\,\text{eV}

This positive value indicates energy must be supplied to the atom.

Answer:

+10.4\,\text{eV}

Option B.

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