5.12 Lecture: Bohr Model of the Atom

What are the energy levels designated by?

A number and the symbol "n". *For example, the 1n shell represents the first energy level located closest to the nucleus.*

Niels Bohr proposed what?

An early model of the atom as a central nucleus containing protons and neutrons being orbited by electrons in shells.

Electrons fill orbit shells in what order?

Consistent order.

The second electron shell can each have a maximum of how many electrons?

Eight electrons. Ex: The picture shows the maximum number of electrons for the first three shells.

Light that is emitted directly related to what?

Energy transition. The larger the transition, the greater the energy.

Example of energy transition:

In the image, the yellow light absorbed and moved the electron from the n=2 (2nd shell) to the n=6 (6th shell). Now to come back down to the electron's normal energy shell (2nd shell) it needs to emit energy (as light) to come down to a lower energy level. The transition is related to the light.

Bohr also proposed:

Light radiated from hydrogen atoms only when an electron made a transition from an outer orbit to one closer to the nucleus. The energy lost by the electron in the abrupt transition is precisely the same as the energy of the quantum of emitted light.

The Bohr model of a nitrogen atom shown:

Nitrogen has 7 protons and 7 electrons in a neutral atom (not an ion). Remember, each shell is equal to the row in the periodic table.

What does the Bohr model show?

Shows the atom as a central nucleus containing protons and neutrons with the electrons in circular orbitals at specific distances from the nucleus.

What does quantized mean?

The atom can only have very specific amounts of energy

Under standard conditions, atoms fill which shell first. The inner or outer shell?

The inner shell. It also often resulting in a variable number of electrons in the outermost shell.

What did Bohr amend?

The view of the motion of the planetary electrons to bring the model in line with the regular patterns (spectral series) of light emitted by real hydrogen atoms. By limiting the orbiting electrons to a series of circular orbits having discrete radii, Bohr could account for the series of discrete wavelengths in the emission spectrum of hydrogen.

What does the orbits form?

They form electron shells or energy levels, which are a way of visualizing the number of electrons in the various shells.

The innermost shell has a maximum of how many electrons?

Two electrons.

What is an excited state?

a state in which an atom has more energy than it does at its ground state