Physics · Atoms · NEET
Excitation energy is the minimum energy an electron in an atom must absorb to move from a lower energy level to a higher energy level. For hydrogen, energy levels are E_n = -13.6/n^2 eV. Excitation energy = E_higher - E_lower. Example (ground state n=1 to n=2): E2 - E1 = (-3.4) - (-13.6) = 10.2 eV. This is called the first excitation energy of hydrogen.
Excitation potential is the accelerating voltage that gives an electron just enough energy to excite the atom. Excitation potential (in volts) = Excitation energy (in joules) / charge e. Because 1 eV = e joules, the number is the same: first excitation energy 10.2 eV means first excitation potential 10.2 V. Energy is measured in eV; potential is measured in volts.
Excitation only lifts the electron to a higher orbit that still belongs to the atom (n stays finite). Ionisation removes the electron completely (n goes to infinity, E=0). So ionisation energy of hydrogen from ground state = 0-(-13.6)=13.6 eV, while first excitation energy is only 10.2 eV. Excitation energy is always less than ionisation energy.
Usually yes for standard NEET values (first, second excitation energy start from n=1). But if the atom is already in an excited state, the excitation energy for the next jump is E_final - E_initial from that state. Always read the question: 'first excitation energy' means n=1 to n=2, but a jump like n=2 to n=3 has its own value of (-1.51)-(-3.4)=1.89 eV.
First excitation energy (n=1 to n=2) = -3.4 - (-13.6) = 10.2 eV, so first excitation potential = 10.2 V. Second excitation energy (n=1 to n=3) = -1.51 - (-13.6) = 12.09 eV, so second excitation potential = 12.09 V. Notice second is larger than first because the electron is lifted higher.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
10.2 eV. It is the energy to move the electron from the ground state (n=1, -13.6 eV) to the first excited state (n=2, -3.4 eV): 10.2 eV. The first excitation potential is therefore 10.2 V.
Volt (V). Excitation potential is a voltage. Excitation energy is usually written in electron-volts (eV) or joules (J). The number in volts equals the number in eV.
No. Excitation keeps the electron bound in a higher finite orbit, while ionisation frees it completely (n = infinity). As the target level rises toward infinity, excitation energy approaches but never equals the ionisation energy of 13.6 eV for hydrogen.
Because higher orbits sit closer to zero energy. Jumping from n=1 to n=3 (12.09 eV) covers a bigger energy gap than n=1 to n=2 (10.2 eV), so the second excitation energy is larger.
