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Posted: Fri Nov 29, 2019 5:41 pm
Can someone explain to me how when an photon is absorbed how the change will be positive and not negative?
Posted: Fri Nov 29, 2019 5:54 pm
A photon is absorbed when the energy of an electron increases and its principle quantum number increases. The energy is positive when a photon is absorbed.
Posted: Fri Nov 29, 2019 6:22 pm
When an electron is an infinite distance from the nucleus, we say that the energy is zero. So, when the electron comes closer to the nucleus, the Energy is negative. An electron from a higher to lower principal quantum number will be coming closer to the nucleus, so will become more negative. This will result in a release of energy.
Posted: Fri Nov 29, 2019 6:32 pm
Just think of it in relation to the nucleus. If an electron is emitted aka going away, it's a negative energy value. If it is being absorbed and coming closer, it is positive.
Posted: Sun Dec 01, 2019 11:25 am
You can also think of this in terms of the potential energy equation. (PE=q1q2/r). R is the distance between the electron and nucleus. As R gets bigger and bigger, potential energy approaches 0.
As an electron goes farther from the nucleus it reaches higher energy levels and approaches 0 or becomes more positive. We can know think of it in the opposite sense. As an electron moves towards the nucleus, the change in energy must be negative because it is reaching lower potential energy levels. This change in negative energy is shown as atoms emit a photon when electrons move from higher levels to lower levels.