Chemistry · Structure Of Atom · NEET
It is a choice of reference point. We agree that a free electron, resting far away (at infinity) with no attraction to the nucleus, has energy = 0. The nucleus attracts the electron, so when the electron falls into an orbit, work is done by the attraction and the electron ends up with energy LOWER than zero. Lower than zero means negative. So the minus sign is not a mistake - it simply says the electron is trapped and has less energy than a free electron.
No. Negative here does not mean 'less than nothing' in a physical sense. It only means 'below the reference level we picked (zero at infinity)'. Think of it like temperature below 0 degrees Celsius - it is still a real temperature, just below the mark we called zero. Same idea: -13.6 eV is a real amount of energy, just below the free-electron level.
The negative sign tells you the electron is BOUND to the nucleus. To pull it out of the atom, you must ADD energy to bring it back up to zero. For hydrogen ground state, E = -13.6 eV, so you must supply +13.6 eV to free it. This is exactly the ionisation energy. So the negative sign is directly linked to how tightly the electron is held.
Because energy = -RH/n squared. When n is small (n=1), you divide by 1, so the number is large and very negative (-13.6 eV). When n is bigger (n=2), you divide by 4, so it is closer to zero (-3.4 eV). As n goes to infinity, energy goes to 0. So closer orbits are more negative and more tightly bound.
More negative = more stable. The lowest (ground) state n=1 has the most negative energy and is the most stable. A more negative number means the electron is held more tightly and needs more energy to be removed. This is a very common NEET trap - do not confuse 'more negative' with 'higher energy'. More negative actually means LOWER energy.
When the electron just barely escapes (reaches infinity with zero speed), its energy becomes 0 - the reference level. If you give it even more energy, it becomes a free electron with positive kinetic energy. So the ladder goes: very negative (bound, ground state) up to 0 (just freed) up to positive (free and moving).
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The zero point is a free electron at infinite distance from the nucleus, at rest, with no attraction. Any electron bound inside the atom has energy below this, so its energy is negative.
It is -13.6 eV (or -2.18 x 10^-18 J) for n=1. The negative sign shows the electron is bound; +13.6 eV must be added to remove it, which equals the ionisation energy.
It appears for every atom's bound electron in the Bohr model. The formula En = -RH x (Z squared / n squared) always gives a negative value because the electron is attracted and bound. Higher Z just makes it more negative.
No. A bound electron always has negative energy. Once its energy reaches zero or positive, it is no longer bound - it has escaped the atom and become a free electron.
Ionisation energy is the energy needed to raise the electron from its negative level up to zero (free). For hydrogen ground state, that is +13.6 eV, the exact opposite of the -13.6 eV bound energy.
