1. By: Chris Mavila, Grace Ogden, and Sam Margolis
Niels Bohr
Models of the Atom
By: Chris Mavila, Grace Ogden, and Sam Margolis

2. The Problem
Rutherford’s previous accepted model of the atom described the electron
It was depicted as an orbiting planet
This model portrayed electron particles moving in circular paths

3. The Problem (continued)
The particles would have to be accelerating
Accelerating electrons create a changing magnetic field
Magnetic fields carry away energy from electrons
The electrons slow down and eventually become captured by the nucleus, destroying the atom

4. Experimental Design Built upon spectroscopic observations of atoms
Argued that the energy of a bound electron is quantized
Energy can be added to atoms to form a new energy level
They would then have to give off energy
This is addressed to be the true origin of light
Proposed neutrons and protons occupy a dense central region called the nucleus
Electrons orbit the nucleus like planets orbiting the sun

5. Evidence that the previous model was incorrect
Rutherford’s (previous model of solar system) model would mean that the orbiting electrons would lose energy, give off radiation, and crash into the nucleus, ultimately destroy the atom.
Bohr knew Rutherford’s model must be wrong considering how long atoms last and how stable they usually are.
The radiation shown in Rutherford's model would mean a continuing spectrum of every color (white light) would be produced. However, when pure gases of different elements combine are excited with electricity, radiation of different frequencies is given off, thus producing distinct, different colors, not white light.

6. The Bohr Model
Electrons exist at quantized energy levels, meaning they are set in orbit at fixed distances from the nucleus
The higher the energy-level number, the farther away the electron is from the nucleus
An electron’s normal energy level is called its ground state
If an electron absorbs energy, it becomes excited and moves to a higher energy level
If an electron releases energy, it moves to a lower energy level

7. Noteworthy Niels Won a Nobel Prize at age 37 (year was 1922)
Put forth the theory of the nucleus as a liquid drop and the idea of things having dual natures
One of his six sons also won a Nobel Prize
Founded the Institute for a Theoretical Physics of the University of Copenhagen in 1920, which was later named after him (now called the Niels Bohr Institute)
Helped found the European Organization for Nuclear Research

8. Sources