Mohave Quiz Chapter 6.1-6.4
Complementary Properties (position and velocity)
Position and velocity are said to be complementary properties: the more you know about one, the less you know bout the other.
What equation is used to calculate the speed of waves (EMR)?
Speed of electromagnetic radiation = wavelength x frequency - c = lambda x nu
Wavelength
The distance between successive peaks
Blamer Series
The four visible lines hydrogen emits when its electrons are excited.
Frequency
The number of waves that was a particular point per second. - the number of waves passing a given point per unit of time (symbol: nu). - unit of frequency: Hz or # per second
Emission spectra
There are two types of emission spectra: continuous and line. - A spectrum consisting and containing light of all wavelengths is called a continuous spectrum. - a spectrum containing radiation of only specific wavelengths is called a line spectrum.
Line Spectra
There are two types of line spectra: emission and absorption - a spectrum containing radiation of only specific wavelengths.
Wavelength vs Velocity: what happens when one is greater than the other?
- The greater the wavelength, the smaller the frequency. - The smaller the wavelength, the greater the frequency.
What is value for hcR?
hcR = -2.18 x 10^-18 J
How to calculate wavelength
wavelength = c/v = hc/change in energy
What is the equation for the wavelength of matter by De Broglie?
wavelength = h/mv where v = velocity and m = mass
Black Body Radiation
- black body is an object that can absorb or reflect any and all different radiations. *this is a theoretical object since no such object exists. - black body radiation is when an object is heated enough to start emitting its own radiation, which is usually seen as a color. *as you increase the heat or frequency that black body radiation will eventually reach its peak before declining, regardless of if you continue to increase the heat/frequency. *metal absorbs energy from the fame, the atoms in it begin to move in an unstable manner, so to stabilize themselves they release radiation. - Max Planck thought light was given off in discrete chunks, but before this, people thought light was continuous. - light and energy are quantized, not continuous.
How do we know EMR has particle properties?
- black body radiation - photoelectric effect - line emission spectra of elements
Photoelectric Effect
- when light is focused on a piece of metal, it heats the atoms and causes them to release electrons. - each metal has a specific frequency the radiation must have in order for the metal to emit elections. *threshold frequency: minimum frequency that radiation must have to cause the metal to emit electrons. - energy of photons must be enough to break the attraction between the metal's nucleus and electrons. *the frequency needed for metal to emit electrons is decided on/dependent on the strength of attracting between atoms, and then the nucleus and electrons attraction. - when a frequency strong enough to separate electrons from the nucleus, ONE proton from the frequency releases ONE electron from the metal. *when there's left over energy after separating an electron from the metal, that left over energy is released in the form of KE.
Bohr's Model
A long time ago Bohr suggested a planetary model. - a nucleus surrounded by shells of energy (each shell is specific in energy level). - he said electrons can be on any shell (energy level), but could not exist in between them. - energy levels are quantized - electrons don't radiate energy while they are spinning in orbit on an energy level, and that's why they don't spiral into the nucleus.
At what speed does electromagnetic radiation move at?
All electromagnetic radiation travels at the same velocity; the speed of light. - 3.00 x 10^8 m/s
How did Bohr use line emission to explain electrons dropping to different energy levels?
Bohr knew electrons dropped form different energy levels because with line emission, he saw that it wasn't continuous, meaning that electrons could not reside in between the different energy levels.
Bohr Equation
Change in Energy = (hcR)(1/final n^2 - 1/initial n^2) - exactly predicts where the wavelengths of hydrogen appear in the visible spectrum. - shows the difference in energy when an electron goes from one energy level to another.
What is the equation to find the change in energy from one energy level to another?
Change in energy = final energy - initial energy change in energy = planck's constant x nu
What was De Broglie's reason for why we didn't think matter had wavelengths?
De Brolie thought that the reason we didn't know matter had wavelengths was because they were so small and they'd go unnoticed.
What is the formula to calculate the energy of an electron at any specific energy level?
E = (-hcR)(I/n^2) = (-2.18 x 10^-18 J)(I/n^2) - this is the energy an electron possess at any certain level; where n = the specific energy level.
Planck's equation for energy of a photon
E = H(nu) where h = planck's constant and nu = frequency
What duel-nature does EMR have?
EMR has a duel nature: wave-particle duality 1. EMR can have particle properties 2. EMR can have wave behavior
What does it mean for an electron to be in its "ground state?"
Ground state is when electrons are at the lowest available energy level.
Value of Planck's constant
H = 6.626 x 10^-34 Js
What did Heisenberg say?
He said that it is impossible to know simultaneously the exact position and velocity of a particle.
What did Heisenberg propose? The Uncertainty Principle.
Heisenberg proposed that the duel nature of matter places a fundamental limitation on how precisely we can know both the location and the momentum of an object at a given instant. The limitation becomes important only when we deal with matter at the subatomic level.
What idea did Louis de Broglie think of?
If radiant energy could behave as though it were a stream of particles (photons), could matter possibly show wave properties? - he suggested electrons moved about the nucleus like a wave and, therefore, had wavelength. *he proposed that the wavelength of electrons, or any other particle, depends on its mass and velocity.
Are wavelength and frequency reported as positive or negative quantities?
Wavelength and frequency are ALWAYS reported as positive quantities.
How do we know EMR has wave properties?
We know EMR has wave properties because of diffraction. - anything that can be diffracted has wave properties. - we observed diffraction in EMR and thats how we know that it has wave properties. *Diffraction is when light or EMR are trying to go through a small opening and constructive or destructive interference occurs. - if matter/particles have wave properties, then we must be able to see diffraction.
How do we know light has particle properties: black body radiation?
We know light has particle properties because it is not continuous, but quantized, given off in small chunks (think stairs).
How is energy emitted to produce a line effect (line emission)?
When electrons are at the highest energy level, they are unstable and thus, they drop to a lower energy level to become more stable. One eaten drop from a higher energy level, they release energy, and the released energy appears as colors. - Different colors are emitted dependent on which energy level the electrons drop from.
What does it mean for an electron to be "excited?"
When electrons are elevated to a higher energy level than the lowest, the electrons are consider "excited."
When n = infinity, what is the energy of the electron?
When n = infinity, the energy of the electron is 0 because it has left the nucleus.
Destructive interference
When peaks of a wave and toughs of a wave overlap.
How do you know there will be constructive interference?
When the distance between/thickness of an object is an integer and light is reflected off it, you know there will be constructive interference.
What can we deduce when we apply the uncertainty principle to electrons?
When the uncertainty principle is applied to the electrons in an atom, this principle states that it is impossible for us to know simultaneously both the exact momentum of the electron and its exact location in space.
What properties are you looking at when you are focused on the location of an electron? What properties are you looking at when you are focused on the speed/energy of an electron? (Heisenberg)
When we are looking at the location of an electron, we're looking at the particle properties. If we're looking at the energy/speed of the electron, we are looking at its wave properties.
Constructive interference (waves)
Where waves overlap its called constructive interference.
