Why are electrons placed in energy levels and sub-levels?
In: Chemistry
This is actually a very complicated question. The full answer involves quantum mechanics.
The shortest answer is basically that when a particle is free (unbound), like a single electron existing alone in some infinite empty universe, it can have any energy it wants. The energies it can have are continuous: 1.1 eV, 2.7 eV, 1.1000001 eV, and anywhere in between and beyond. Like the real numbers.
However, due to quantum mechanics, when things become bound, their energies become quantized. I.e. the energies they are physically allowed to have are no longer continuous, but instead discrete values (e.g. 1 eV, 1.5 eV, 1.7 eV). Based on their environment and the system they’re in and the relevant quantum numbers and so forth, a particle can exist in any number of given energy levels, but NOT anywhere in between.
This gets way more complex (and always way more interesting!) but requires a depth I think is probably outside the scope of ELI5. Feel free to ask additional specifics, though.
The other comment already mentioned that electron energies are quantized in the atomic bound state. In the atom, the behavior of electrons must be represented with waves.
Within each energy level, electrons occupy certain orbitals with very strange shapes of the probability density! The waves of a vibrating string are a familiar sight. But it’s less intuitive to picture the kinds of [“waves”](https://en.wikipedia.org/wiki/Spherical_harmonics) that occupy 3-D space around a center *point*.
Latest Answers