Why are the energies different? What does the model explain?
In a model of electron arrangement consistent with experimental data, electrons exist only in specific (discrete) energy states.
The allowed energy states are referred to as energy levels (shells).
For the first 20 elements in the periodic table, the electrons may occupy up to four energy levels (shells).
In the ground (normal) state of the atom, the electrons occupy the levels (shells) in such a way that the overall energy of the atom is minimised.
These are a bit like climbing a ladder, you are only specific heights above the ground (not between the rungs).
Note that the difference in energy between the levels (shells) is not the same and is lower for higher energy levels (shells).
Note that the difference in energy between the levels (shells) is not the same and is lower for higher energy levels (shells).
The allowed energy states are referred to as energy levels (shells).
For the first 20 elements in the periodic table, the electrons may occupy up to four energy levels (shells).
In the ground (normal) state of the atom, the electrons occupy the levels (shells) in such a way that the overall energy of the atom is minimised.
We will see later that some of our shell-hotels have more rooms available than others!
The energy associated with each energy level (shell) depends on how far, on average, its electrons are from the nucleus.
Energy levels (shells) having electrons more distant from the nucleus are of higher energy because, as the diagram shows energy is required to separate the negative electrons from the positive nucleus.
What are the experimental results that this model explains?
Only some of the electrons on the atom are involved in bonding to other atoms.
Only the electrons in the levels of highest energy (farthest from the nucleus) can be shared with or transferred to other atoms.
Atoms only absorb energy that corresponds to a difference in their energy levels.
An electron in energy level 1 can only be excited to energy level 2 or 3 or 4, not to any intermediate energy level.
After the source of energy is removed, the excited electron returns to energy level 1 (the ground state) with emission of energy in the form of light.
Through measurement of the energy associated with the light emitted, scientists have been able to determine the differences in energy between the energy levels.
After the source of energy is removed, the excited electron returns to energy level 1 (the ground state) with emission of energy in the form of light.
Through measurement of the energy associated with the light emitted, scientists have been able to determine the differences in energy between the energy levels.