Quantum Theory Objectives: Compare the particle to wave model of light Compare the particle to wave model of light Analyze the path of the electron Analyze the path of the electron Contrast the spectra Contrast the spectra Identify the quantum numbers that lead to the locations of the electrons Identify the quantum numbers that lead to the locations of the electrons Write electron configurations and Write electron configurations and Define the parts of the configuration such as the valence Define the parts of the configuration such as the valence

Facts So, we know what is in the nucleus. So, we know what is in the nucleus. Protons and neutrons Protons and neutrons Most of the mass of the atom lies here Most of the mass of the atom lies here How do the electrons exist outside the nucleus? How do the electrons exist outside the nucleus? How do electrons occupy the space surrounding the nucleus? How do electrons occupy the space surrounding the nucleus? How do they avoid the laws of physics? (repulsion) How do they avoid the laws of physics? (repulsion)

The electromagnetic spectrum (above) illustrates the visible light portion of electromagnetic radiation. The electromagnetic spectrum (above) illustrates the visible light portion of electromagnetic radiation. What energy type comes after the violet? What energy type comes after the violet? What energy type comes after the red? What energy type comes after the red? Which one has the most energy? Least? Which one has the most energy? Least?

Fact Sheet 2 Electromagnetic waves can be described by their wavelengths, energy, and frequency. Electromagnetic waves can be described by their wavelengths, energy, and frequency. All three of these things describe a different property of light, yet they are related to each other mathematically. All three of these things describe a different property of light, yet they are related to each other mathematically. Wavelength is usually measured in meters (m). Wavelength is usually measured in meters (m). Frequency is the number of cycles of a wave to pass some point in a second. The units of frequency are thus cycles per second, or Hertz (Hz). Frequency is the number of cycles of a wave to pass some point in a second. The units of frequency are thus cycles per second, or Hertz (Hz). All light travels at the same speed, but each color has a different wavelength and frequency. It is their different wavelengths that cause the different colors of light to separate and become visible when passing through a prism.

Let’s analyze the wave:

Waves in the electromagnetic spectrum vary in size from very long radio waves the size of buildings, to very short gamma-rays smaller than the size of the nucleus of an atom

Illustration of frequency: Look at the illustration of the visible spectrum above. Can you guess which color has the longest wavelength?

Frequency vs. Wavelength Based on prior knowledge, just how do these two relate? Based on prior knowledge, just how do these two relate? Why can we use these terms to discuss anything on the electromagnetic spectrum? Why can we use these terms to discuss anything on the electromagnetic spectrum?

Mathematical Relation Speed = Wavelength * Frequency

Materials: Materials: set of red, green and violet (purple) pencils set of red, green and violet (purple) pencils manila folder meter stick or metric ruler manila folder meter stick or metric ruler pair of scissors pair of scissors 4 books 4 books watch with second hand watch with second hand one strip of masking tape one strip of masking tape extra pencil extra pencil LAB: Obj: You will construct a simplified model of different light waves in order to determine a constant relationship between wavelength and frequency.

We already know that light acts like a wave, but did you know that sometimes it acts like a particle? We call particles of light photons. Low-energy photons, like radio photons, tend to behave more like waves, while higher energy photons (i.e. X-rays) behave more like particles. That's another reason that we don't talk about X-ray waves very often. Instead we talk about individual X-rays and their energies. We already know that light acts like a wave, but did you know that sometimes it acts like a particle? We call particles of light photons. Low-energy photons, like radio photons, tend to behave more like waves, while higher energy photons (i.e. X-rays) behave more like particles. That's another reason that we don't talk about X-ray waves very often. Instead we talk about individual X-rays and their energies.

Atomic Emission Spectra When matter is heated, it gives off light. For example, turning on an ordinary light bulb causes an electric current to flow through a metal filament which heats the filament and produces light When matter is heated, it gives off light. For example, turning on an ordinary light bulb causes an electric current to flow through a metal filament which heats the filament and produces lightlight heatslight heatslight The electrical energy absorbed by the filament excites the atoms' electrons causing them to 'wiggle'. This absorbed energy is eventually released from the atoms in the form of light. The electrical energy absorbed by the filament excites the atoms' electrons causing them to 'wiggle'. This absorbed energy is eventually released from the atoms in the form of light.energyelectronsenergyatomslightenergyelectronsenergyatomslight

Neon line spectra Neon line spectra Bohr knew that when pure elements were excited by heat or electricity, they gave off distinct colors rather than white light. This phenomenon is most commonly seen in modern day neon lights, tubes filled with gaseous elements (most commonly neon). When an electric current is passed through the gas, a distinct color (most commonly red) is given off by the element. When light from an excited element is passed through a prism, only specific lines (or wavelengths) of light can be seen. These lines of light are called line spectra. Bohr knew that when pure elements were excited by heat or electricity, they gave off distinct colors rather than white light. This phenomenon is most commonly seen in modern day neon lights, tubes filled with gaseous elements (most commonly neon). When an electric current is passed through the gas, a distinct color (most commonly red) is given off by the element. When light from an excited element is passed through a prism, only specific lines (or wavelengths) of light can be seen. These lines of light are called line spectra.elements heatlightelementselementlightelementwavelengthslight elements heatlightelementselementlightelementwavelengthslight

When an atom is excited, such as during heating, electrons can jump to higher levels When an atom is excited, such as during heating, electrons can jump to higher levelsatom electronsatom electrons Bohr hypothesized that electrons occupy specific energy levels. Bohr hypothesized that electrons occupy specific energy levels.electronsenergyelectronsenergy When the electrons fall back to lower energy levels, precise quanta of energy are released as specific wavelengths (lines) of light. When the electrons fall back to lower energy levels, precise quanta of energy are released as specific wavelengths (lines) of light.electronsenergy wavelengthslightelectronsenergy wavelengthslight

The comfy spot for an electron is on the ground state which is the lowest energy level in the atom The comfy spot for an electron is on the ground state which is the lowest energy level in the atom Key to Bohr's theory was the fact that the electron could only 'jump' and 'fall' to precise energy levels, thus emitting a limited spectrum of light. These pockets of energy are called “quanta”. Key to Bohr's theory was the fact that the electron could only 'jump' and 'fall' to precise energy levels, thus emitting a limited spectrum of light. These pockets of energy are called “quanta”. electron energylight electron energylight

Bohr also predicted that those levels had limits to the number of electrons each could hold. Bohr also predicted that those levels had limits to the number of electrons each could hold.electrons This leads us to the Quantum Theory This leads us to the Quantum Theory