# Question about the Bohr model of atom and and electron in an orbital

• I
I have a question about what happen when an electron in the Bohr model of atom, gains energy because for example is "hitting" by a photon.
Electron have an energy, and it is the sum of potential and kinetic.
When they gain energy, they gain potential energy so they go further away from nucleus and become slower, or they gain kinetic energy so they become faster but near to nucleus? and why?
thanks

PeroK
Homework Helper
Gold Member
2020 Award
I have a question about what happen when an electron in the Bohr model of atom, gains energy because for example is "hitting" by a photon.
Electron have an energy, and it is the sum of potential and kinetic.
When they gain energy, they gain potential energy so they go further away from nucleus and become slower, or they gain kinetic energy so they become faster but near to nucleus? and why?
thanks
In general, the greater the energy the further the electron is from the nucleus. This is true for QM atomic orbitals - and also true for classical orbits in an inverse square potential.

In general, the greater the energy the further the electron is from the nucleus. This is true for QM atomic orbitals - and also true for classical orbits in an inverse square potential.
Thank you
But my question is because for an energy E i think there is ( if the orbit is circular with a definite radius r) an "infinite" amount of pairs of velocity and distance (v,r) with the same energy, so in what way when energy increase the electron be?
higher speed? higher potential?

PeroK
Homework Helper
Gold Member
2020 Award
Thank you
But my question is because for an energy E i think there is ( if the orbit is circular with a definite radius r) an "infinite" amount of pairs of velocity and distance (v,r) with the same energy, so in what way when energy increase the electron be?
higher speed? higher potential?
Unlike the classical case, the orbitals are not well-defined trajectories. So, you have to calculate the expected values of ##r## and kinetic energy. These, however, follow the same principle that higher energy levels correspond to a greater expected value of ##r##.

It should be clear that if you give an electron too much energy then the atom is ionised and the electron is released - i.e. the energy takes it beyond any bound orbital.

Unlike the classical case, the orbitals are not well-defined trajectories. So, you have to calculate the expected values of ##r## and kinetic energy. These, however, follow the same principle that higher energy levels correspond to a greater expected value of ##r##.

It should be clear that if you give an electron too much energy then the atom is ionised and the electron is released - i.e. the energy takes it beyond any bound orbital.
Maybe is the fact that higher energy levels correspond to a greater expected value of r, why the electron doesn't become only "quicker" around the orbit?

PeroK
Homework Helper
Gold Member
2020 Award
Maybe is the fact that higher energy levels correspond to a greater expected value of r, why the electron doesn't become only "quicker" around the orbit?
... because the orbitals must satisfy the Schroedinger equation.

... because the orbitals must satisfy the Schroedinger equation.
Ok.... that is.
Thank you

DrDu