The model of the atom that is consistent with experiment has a nucleus containing the protons and neutrons at the center of an electron cloud.
The number of electrons on an atom is given by the atomic number in the periodic table.
The nucleus is very small in comparison to the volume of the atom.
Electrons occupy most of the volume of the atom.
Rolling your mouse over the image shows an expanded view of the nucleus.
Electrons occupy most of the volume of the atom.
Rolling your mouse over the image shows an expanded view of the nucleus.
The number of electrons on an atom is given by the atomic number in the periodic table.
In a model of electron arrangement consistent with experimental data, electrons exist only in specific (discrete) energy states.
This model for electron energy distribution is quite different from the model, also shown, where electrons may have any energy. 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 lowest energy levels (shells) possible.
Why is the energy of the various energy levels (shells) different?
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 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.
Atoms only absorb energy that corresponds to a difference in their energy levels.
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 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 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.