Neils Bohr
1885-1962 Bold new theory as to why electrons were not “captured” by the nucleus
Electrons in an atom can only contain certain energies Energy levels Therefore, electron energy is said to be quantized. Each energy level is a fixed distance from the nucleus.
Often described as spherical shells arranged concentrically. According to Bohr, an electron with a particular amount of energy will travel along a 3-dimensional pathway called an orbit. Often described as spherical shells arranged concentrically.
Shells are designated by a principal quantum number, n, which can be any positive integer from 1 to infinity.
Bohr’s assumptions An electron can travel indefinitely within an energy level and not lose energy; The greater the distance between the nucleus and an energy level, the greater the energy required for an electron to be in that energy level; An electron cannot exist between orbits, but can move to a higher, unfilled orbit if it absorbs a specific quantity of energy. Same is true for a lower (unfilled) orbit if the electron loses a specific quantity of energy.
Jumping = “transition” The energy absorbed is equal to the difference in energy between the 2 energy levels. The energy released is equal to the difference in energy between the 2 energy levels. Jumping = “transition”
When an electron is in the lowest energy level it can occupy, we say it is in the ground state. When all the electrons of an atom are in the lowest possible energy levels, we say the atom is in ground state.
Where did this all come from?? Experiments with hydrogen
When the violet light was passed through a prism, it separated into a series of coloured lines called a line spectrum.
White light?
What does this have to do with Bohr? He thought that what happened was this: When energy was supplied to the hydrogen electrons, they jumped from a lower energy level to a higher energy level. As they dropped back to lower energy levels, they released energy that corresponded to specific wavelengths (which we see as visible light!)
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