Units 14-15 Flashcards
True or False: The molecular model tells us something about the internal structure of molecules.
FALSE
True or False: Electrons have the same mass and charge in every type of atom.
True
Which part of the atom determines the unique nature of the atom?
The positive part.
True or False: Protons have the same mass and charge in every type of atom.
FALSE
Same charge, different mass
Which has smaller mass, electron or proton?
Electron
What is the Plum Pudding model?
The positive charge is spread equally throughout the atom. Electrons are sprinkled throughout the positively charged region.
What are alpha particles?
High energy, positively charged particles. Can break apart atoms.
It’s a helium nucleus emitted in radioactive decay.
True or False: The atomic nucleus is INCREDIBLY dense
True
Is the nucleus positive or negative?
Positive
What is the solar system model of the atom?
A model of the atom in which the electrons orbit the small, dense, positively charged nucleus in elliptical paths.
What is an emission spectrum?
The set of colors of light given off, or emitted by, an object.
Not always a rainbow
What are discrete emission spectra?
Spectra that don’t give off a rainbow, selective colors based on the properties of the materials.
What are emission lines?
The sharp, easily identifiable lines of emission from discrete emission spectra
True or False: The colors in the spectrum of a hot object depend only on the object’s temperature, not its material composition.
TRUE
True or False: Hot objects glow at all wavelengths
True
True or False: When atoms change from a high energy state to a low energy state, they emit the energy difference (conservation of energy) as light.
True
True or False: The colors in the spectrum of an object being heated depend only on the temperature and not on its material composition
True
True or False: Discrete colors = discrete energies
True
What does quantized mean?
The number of possible values has been restricted.
Quanta, quantum, quantized = some kind of restriction on the possible values, discrete
What properties of atoms have a dependence on discrete integers (quanta)?
Angular momentum
Energy
What is the modified solar system model?
AKA the Bohr model. With restricted circular orbits of electrons around a nucleus.
Takes Quanta integers into account (discrete)
What does n represent in the Bohr model?
The radius (distance) between the electron and the nucleus
What happens to the energy and radius of the electron orbit as the quantum number increases?
They increase
True or False: Electrons can occupy the space between the quantum orbits.
FALSE
They are restricted to their specific orbit
What is the postulate of quantization of the Bohr model?
Any electron in an orbit (n) possesses a specific energy.
How do electrons lose energy and fall down to a lower n state?
By emitting energy as a photon of LIGHT.
What determines the frequency and color of the light that is emitted by an electron?
It is the energy difference between the two orbits.
Energy of outer orbit - energy of inner orbit = energy of emitted photon.
True or False: Violet photons are more energetic than red photons
True
Where does the energy come from that causes electrons to be in a higher state (n orbit)?
Collisions.
What is an excited state?
A high n orbit.
Anything other than the lowest n
Other than collisions, what is a way that electrons jump up to higher states?
By absorbing passing photons. They absorb that energy.
What is the reverse process of photon emission?
Photon absorption
What do black gaps represent on a spectra when white light is passing through a tube containing gas?
Absorption is occurring.
The black gaps are the exact same colors that would appear if the electrons were EMITTING photons.
What is one problem with the Bohr model?
It works perfectly for Hydrogen, but doesn’t work for all other elements.
True or False: In the Bohr model, the electrons are accelerating charges.
True
Do accelerating charges emit radiation?
YES
True or False: Bohr’s model correctly explains why angular momentum should be quantized.
FALSE
He gave no explanation for it. There’s no justification for his predictions.
What was revolutionary about the step between the Bohr and Rutherford models?
Bohr added the idea that nature operates with discrete quantization rather than continuous energies and momentum. (circles, not ellipses)
What is an absorption spectrum?
The set of dark lines that are missing from a continuous spectrum of light after the light has passed through a gas.
What is an emission spectrum?
The set of colors of light given off (or emitted) by an object.
What is an ion?
A charged atom or molecule
What defines the state of an electron?
Its energy level
Who came up with the plum pudding model?
Thompson
Why did the alpha particles reflect off the gold foil?
Rutherford learned that the positive alpha particles must be being repelled by a super dense positive thing in the middle of an atom. So MOST of the time, the particles would go through (the empty/electron space) but occasionally they would hit the superdense positive nucleus in the middle and reflect back.
What are other names for the Rutherford model?
The nucleus model or the solar system model
How is the energy of a Photon measured?
Planck’s constant times its frequency
How do you measure the wavelength of matter?
w = h/p
h = planck’s constant
p = momentum
Why don’t we notice the wavelengths of human sized things? Matter that we’re familiar with like water droplets or balls?
Because it’s soooooooo small.
What is quantum mechanics?
The branch of physics used to describe the wave properties of light and matter.
All matter is not just a particle, it’s also a wave.
Can Newton’s equations explain the motion of an electron in an atom?
Nope, too small and deals with weird waves
True or False: Electrons function as waves.
True
True or False: Electrons exhibit like photons of light, both as waves and particles.
TRUE
True or False: Atoms, neutrons, protons, etc. all behave like both waves and particles
TRUUUUEEE
What is a probability wave?
It tells us the PROBABILITY of where the electrons are likely to be detected (in a double slit experiment).
Basically a probability curve that moves in time and space.
High wave = most likely to be found there
What is a probability curve?
A curve giving the probability of where an object might be detected.
What’s the difference between a probability wave and a probability curve?
A probability wave is expressed in a probability curve
True or False: When an electron passes through a double slit, we can predict exactly where it will strike the screen.
FALSE
Does the most probable place to find a moving electron change with the passing of time?
YES. Because it’s moving, so the position changes. This changes the probability
When is the probability of an electron position at 100%?
When it has struck the screen and can be measured at a SPECIFIC place.
When is the probability of an electron’s position 0%?
When it has struck the screen and we know it can no longer hit any other place.
Aside from position, what properties of a particle do probability curves and waves describe?
Momentum, energy, etc.
True or False: Probability waves of different properties of the same particle are related.
True
What is the Heisenburg Uncertainty principle?
It is impossible to precisely determine both the position and momentum of a small particle at the same time.
What is the relationship between position and momentum as defined by the Uncertainty principle?
Inverse
What is the relationship between wavelength and momentum as defined by the Uncertainty principle?
Direct relationship.
Proportional.
True or False: An experimenter can know a particle’s position with high accuracy and how fast it is going at the same time.
FALSE
One or the other, not both. Heisenburg.
What is the fundamental difference between quantum mechanics and Newton’s laws of motion? (both describe motion)
Quantum mechanics describes the PROBABLE location and motion of objects. Newton’s laws are more precise.
True or False: We can determine an object’s history or future from measurements made in the present under the laws of quantum mechanics.
FALSE
What debate about position and randomness does the picture of a ship in the fog represent? What two sides are represented?
- One could argue that the ship exists, we just don’t know where it is because we don’t have enough information.
- One could also argue that the exact location of the ship is intrinsically UNKNOWABLE and that the act of measuring it causes it to appear someplace.
When are particle properties evident?
When the matter is detected.
When are wave properties (interference and diffraction) evident?
When objects travel.
What does the Heisenberg uncertainty principle say about the relationship between position + momentum and Planck’s constant?
The two must be greater than or equal to Planck’s constant.
How small is the wavelength of an ordinary object?
A fraction of the diameter of an atom. SOOOOO small.
