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CEM 141
Exam 2 Flashcards
| Question | Answer |
|---|---|
| examples of electromagnetic radiation. | radio waves, microwaves, infrared, visible, ultraviolet, x-rays, gamma rays. |
| how do we characterize electromagnetic radiation? | different wave lengths, different frequencies, and different energies. |
| what models are used to describe the behavior of light (electromagnetic radiation)? | a wave and a particle. |
| higher amplitude = ________ . | more intense/brighter light. |
| wavelength determines what? | what type of light you have. |
| as wavelength changes so does ________. | frequency |
| frequency ________ as wavelength shortens. | increases |
| frequency and wavelength have a ________ relationship. | inverse |
| amplitude : | height of peaks (intensity). |
| wavelength : | distance between to identical points. |
| frequency : | number of wave fronts per second. |
| wavelength and frequency are related by the ________. | speed of light. |
| what is the equation for wavelength and frequency? | speed of light = (wavelength) x (frequency) |
| energy of light ________ as frequency increases and as wavelength shortens. | increases |
| true or false: energy of light is related to amplitude. | false |
| which electromagnetic radiation has wavelengths on the order of the sizes of atoms? | X-rays |
| evidence that light is also a wave is that waves ________ and particles don't. | diffract |
| properties of waves in-phase: | peaks and troughs line up (higher amp/brighter) |
| properties of waves out-of-phase: | peak of one wave lines up with the trough of another wave (cancel out - no amp, dark) |
| what is the relationship between the velocity of the wave, the wavelength, and the frequency? | the velocity of the wave is the speed of light. The relationship is that the speed of light (velocity) = the wavelength times the frequency. |
| as you increase the frequency of a wave what happens to the wavelength? | the wavelength shortens because the wave is occurring more frequently. wavelength and frequency have an inverse relationship. |
| which has the longest wavelength: X-rays, visible light, infrared rays | infrared (it has the lowest frequency) |
| which has the highest frequency: X-rays, visible light, infrared rays | X-rays (it has the highest energy) |
| true or false: energy increases with intensity. | false amp (intensity) doesn't define energy, frequency does |
| higher frequency light (and shorter wavelength) has ________ energy. | higher |
| what is the evidence that light is also a particle? | the photoelectric effect |
| what is the photoelectric effect? | it is when light hits a piece of metal causing it to release an electron. |
| how does the photoelectric effect work? | the light is transferring energy to the electron(s) at the metal surface where it is transformed into kinetic energy that gives the electron(s) enough energy to "leave" the atoms in the metal. |
| why are electrons stuck on atoms in the first place? | they're attracted to the nucleus and to break that attraction you have to add energy. |
| when you increase the intensity of ultraviolet light: | the number of electrons emitted increases |
| you keep the intensity the same and increase the wavelength of the blue light: | no change (but increasing the wavelength does decrease the frequency) |
| you keep the intensity the same and increase the wavelength of the yellow light: | zero electrons emitted |
| you keep the yellow light and increase the intensity: | zero electrons are emitted |
| when light shines on a metal surface the outcome depends on the ________ of the light. | frequency |
| if the frequency of light is above the threshold frequency electrons are _________. | emitted from the metal (creates a current) |
| when the intensity (brightness) of the light is increased ________ electrons are emitted. | more |
| if the frequency of the light is below the threshold frequency, ________ electrons are emitted. | no (there's no current) |
| if the frequency of light is below the threshold frequency, will it emit electrons if you increase the intensity? | no, it doesn't matter how intense (bright) the light is electrons are never emitted if the frequency of the light is below the threshold frequency |
| what is the evidence that light is not just a wave that it's also a particle? | if light were just a wave, then increasing the intensity of the light should increase the energy of the light, and with bright enough light of any frequency electrons should be emitted. BUT THIS DOESN'T HAPPEN, because light is also a particle |
| Einstein found that light must come in packets of energy called ________. | photons |
| the energy of a photon is ________. | quantized |
| what does it mean when we say the energy of a photon is quantized? | it can only have certain values |
| the energy of light depends on the ________ not on the intensity. | frequency |
| what is the equation for energy of a photon? | energy of a photon = (planks constant) x (frequency) |
| what is planks constant? | h = 6.626 x 10^ - 34 Js |
| each photon has a ________ energy. | definable |
| when a photon with a definable energy hits the metal, it transfers its energy to an ________. | electron |
| if the photon has enough energy, it can ________. | eject one electron |
| if the photon doesn't have enough energy ________. | no electron is ejected |
| what type of light is required to break a hydrogen molecules covalent bond? | ultraviolet (high energy) |
| when an atom emits light, we see ________. | strips of color and the rest of the spectrum is dark |
| when an atom absorbs light, we see ________. | strips of dark and the rest is the colorful spectrum. |
| light from one particular element does ________ all the colors of the spectrum, it has ________. | not contain, only a few wavelengths |
| atomic absorption and emission spectra show light only of ________ wavelengths/energies. | specific |
| what is Rutherford's model of the atom? | electrons circling nucleus like planets around the sun |
| does the Rutherford model of the atom explain atomic absorption and emission spectra? | no |
| what is the Bohr's model? | electrons move in orbits around the nucleus, each orbit is bigger than the last and has a higher energy than the last. |
| in Bohr's models the orbits have ________ energies and are at ________distances from the nucleus. | definite, definite |
| Bohr explained emission and absorption spectra be invoking _________ energy levels, characterized by ________ numbers (n). | discreate, quantum |
| in Bohr's model photons are emitted or absorbed by atoms as electrons move from _________. | one energy level to another |
| the energy of the photons corresponds to the ________ in energy between the orbits. | difference |
| if a photon is added its energy must equal: | the difference in energies between orbits |
| is Bohr's model an accurate model of the atom? | no, it only works for hydrogen |
| what is the problem with Bohr's model? | electrons are moving in defined orbits around nucleus at known energy levels and it only works for hydrogen |
| what is a better way to represent the transition of electrons upon absorption or emitting photons? | energy diagrams |
| in an energy diagram each energy level has a ________. | quantum number |
| energy levels are ________ orbits. | not (they represent energy only not distance from electron to the nucleus) |
| which set of transitions would produce an emission spectrum? | atom emitting light, getting rid of energy |
| how are absorption and emission different from the photoelectric effect? | absorb/emit: electron is staying within the atom, just moving levels photoelectric: the electron is actually leaving the atom |
| matter is a ________ and a ________. | wave, particle |
| what is the equation for wavelength in terms of matter? | wavelength = (planks constant) divided by (mass) times (velocity) |
| what is the evidence that electrons are waves? | diffraction and interference pattern of waves of light and electrons. |
| true or false: electrons are circling around the nucleus in orbits. | false |
| true or false: we can't measure accurately both energy and position of an electron and that is why Bohr's model is wrong. | true |
| what must our model of the atom include? | electrons (and all particles at atomic molecular level) have wave-like properties, electrons in an atom can only have certain energies (their energies are quantized) |
| true or false: since we know the energy of the electron, we can't know its exact position. | true |
| Erwin Schrodinger applied quantum mechanics to answer what? | where the electrons are in atoms |
| true or false: quantum mechanics allows us to say exactly where the electrons are in the atom. | false, we can't say exactly where they are however, we do know where they are likely to be found |
| atomic orbitals: | regions of space where electrons with certain quantized energy have high probability of being found |
| principal quantum number (n): | determines energy of orbital and identifies its shell - the larger the number the higher the energy and the larger the orbital |
| angular momentum quantum number (l): | identifies the type of orbital (s,p,d,f, ...) and subshell |
| magnetic quantum number (m1): | specifies a particular orbital within a subshell (ie the orientation of the orbital) |
| spin quantum number (ms): | spin quantum number (ms): |
| (l) depends on the value of ________. | (n) |
| (m1) depends on the value of ________. | (l) |
| true or false: no two electrons in an atom have the same four quantum numbers. | true |
| what is the shape of an s orbital? | spherical |
| what is the shape of p orbitals? | dumbbell |
| there are ________ orbitals in both the s and p orbitals. | three |
| in a set of d orbitals there are ________ orbitals. | five |
| how many orbitals are in the electron cloud of one atom? | all of the orbitals (s,p,d,etc) overlap within the electron cloud |
| the 4s orbital is ________ energy than 3d orbital. | lower |
| electrons can be described by orbitals of _______ shapes and ________ energies. | different, definite (this allows us to understand how elements bond and react and the arrangement of the periodic table) |
| alkali and alkaline earth metals are part of the ________. | s-block |
| nonmetals are part of the _________. | p-block |
| transition metals are part of the ________. | d-block |
| we often refer to elements by the location of their electrons in the ________ orbitals. | outermost (valence electrons) |
| core electrons: | low in energy and close to nucleus, within a closed shell (closed shell is very stable, and they don't participate in reactions) |
| valence electrons: | those that are higher in energy, outside closed shell (these are the electrons that determine reactivity) |
| atomic radius: | half the distance between the two nuclei when two atoms are reacting through LDF's |
| atomic radius ________ down a group. | increases |
| what determines the size of an atom | the balance between the attractions of the protons and electrons, and repulsions between the electrons in the atom. (the nucleus pulls electrons in and the repulsions between the electrons push the electrons outward) |
| explain why the atomic radius decreases across the row on the periodic table. | the number of protons and electrons increases. the valence electrons are shielded from full charge of nucleus by core electrons. so, the electrons repel each other and push the electron cloud out. |
| what happens to the atomic radius when an electron is removed from a neutral atom? | atomic radius will decrease. for any atom removing an electron will result in a decrease in amount of repulsive force between electrons, this allows electrons to be drawn closer to the nucleus so the radius decreases. |
| true or false: when you add an electron to a neutral atom the atomic radius increases. | true, repulsive force increases because there's more electrons |
| across a row atomic radius ________ but ionization energy ________. | decreases, increases |
| there is a ________ relationship between atomic radius and ionization energy. | inverse |
| coulomb's law explains: | both attractions between protons and electrons and repulsions between the electrons |
| the atomic radius represents the state where the forces of ________ between electrons and protons are equal to the forces of ________ between electrons. | attraction, repulsion |
| effective nuclear charge: | every valance electron is attracted by the ENC |
| core electrons ________ positive attraction to valance electrons, the valence electrons only get some of the positive attraction force. | blocking |
| core electrons ________ the positive charge from the same number of protons as there are core electrons. | cancel out |
| if the effective nuclear charge increases then the force _______. | increases |
| Columb's law equation for effective nuclear charge: | electrostatic attraction (F) = k (charge of val electron) x (ENC) divided by (distance between the valance electron and the nucleus) |
| atoms with a high ENC hold their electrons ________. | tightly, electrons are more strongly attracted to the nucleus, and this is why AR decreases across a row |
| as you go across a row ENC ________. | stays the same, attractive force is not different but more electrons lead to more repulsions and a larger AR |
| ions are atoms in which ________ have been added/removed. | electrons |
| if an electron is removed from an atom what is the charge of the ion? | positive |
| the ________ electron is removed resulting in a cation. | outermost |
| cations are ________ charged. | positivley |
| if an electron is added to an atom what is the charge of the ion? | negative |
| an electron is added to the ________ orbital. | next available (lowest energy) |
| anions are ________ charged. | negativley |
| ionization energy: | energy required to remove an electron from an atom in the gas phase |
| ionization energy _______ down a group. | decreases |
| ionization energy ________ across a row and ENC also ________. | increases, increases |
| trends down a group: | AR increases, IE decreases |
| trends across a row: | AR decreases, IE increases |
| smaller atoms have ________ ionization energies. | higher |
| the trends in radius and IE are ________ releated. | inversely, but both caused by ENC |
| true or false: it is easier to remove a lone electron from a p orbital than a lone electron from a s orbital. | true, a p orbital is a little farther away from the nucleus than an electron in the s orbital |
| every time you ________ an electron the AR decreases, less electron repulsion. | remove |
| it takes ________ energy to remove a core electron than a valence electron. | much more |
| everything in the universe is moving ________ from us with increasing speed. | away |
| doppler effect: | wavelength depends on what the observer is doing |
| if an object emitting light is moving away from us which direction will the wavelength of the light be shifted? | toward the red end of the spectrum (to longer wavelengths) |
| what happens to the number of atoms over time? | grew rapidly at the beginning and then slowly started to decrease |
| when the __________ takes over the interaction between the nuclei becomes attractive, the PE falls and energy is released into the surroundings. | strong nuclear force |
| if the strong nuclear force did not exist what would happen? | only hydrogen atoms (one proton and no neutrons) would exist |
| what is the evidence that the big bang occurred? | the universe is expanding (red shift) |
| how are nuclear reactions different from chemical reactions? | chemical - involve rearrangement of valence electrons, the identity of the element undergoing the reaction does not change nuclear - involve the nucleus (not electrons), often result in change in element nuclear - |
| isotopes have the ________ number of protons and ________ number of neutrons. | same, different |
| fusion: | adding two nuclei together |
| fission: | breaking a nucleus apart |
| radioactive decay: | emitting particles |
| at ________ nuclear fusion can occur | very high |
| in order for fusion to occur what has to happen? | two nuclei have to collide (this is difficult because they have the same charge, that's why it must be at a very high temperature) |
| strong nuclear force holds ___________. | everything together in nucleus |
| in order for the SNF to come into play the nuclei have to get as close as a distance of about the ________. | diameter of a nucleus |
| when the SNF comes into play what happens to the PE of the system? | decreases (SNF becomes dominant, so they are working with the force) |
| when fusion occurs a lot of energy is ________. | released |
| nuclear reactions are accomplished by changes in ________. | mass |
| during nuclear reactions mass is converted into ________. | energy |
| mass defect: | mass loss (the pieces of isotope don't equal the same as the atom) |
| mass loss is converted into _______. | binding energy |
| how is the total number of atoms in the stars changing over time? | it is decreasing |
| why don't we use fusion reactors instead of combustion (fossil fuels)? | it takes a LOT of energy to start fusion reaction and we haven't managed to get as much energy back out as we put in to start fusion |
| true or false: fission is the opposite of fusion | false, although it is the opposite because it's breaking the nucleus while fusion is adding two together, they both RELEASE energy. |
| nuclear fission: | fragmentation of heavy nuclei to form lighter more stable ones and energy is released |
| critical mass: | mass of the isotope required for the chain reaction to become self-sustaining |
| ________ nuclei undergo fusion to become stable and release energy. | light weight |
| ________ nuclei undergo fission to become more stable and release energy. | heavier |
| radioactivity: | nucleus emits or captures particles of energy in the form of electromagnetic radiation |
| what atoms were formed immediately following the big bang? | hydrogen, helium, and lithium |
| all heavier atoms were formed by ________ in the stars or during the death of a star for elements heavier than iron. | fusion |
| why do bonds form between atoms? | bonds form between atoms because valence electrons are attracted to the nuclei of other atoms. |
| what is the evidence and reasoning that light is a wave? | when light shines through a double slit a pattern of bright and dark lines appear. waves of light interfere constructively when they arrive in-phase and destructively when they arrive our-of-phase. |
| true or false: the absorption lines for hydrogen would appear at exactly the same wavelengths because the energies of the photons emitted and absorbed by hydrogen are the same. | true |
| which energy has a longer wavelength: E= 1 x 10^-12 or E= 1 x 10^-19? | E= 1 x 10^-19 the longer the wavelength the less energy it has because wavelength and frequency have an inverse relationship |
| what is the evidence that supports the claim that light is a particle? | when light shines on metal there is a threshold frequency below which no electrons are ejected from a metal. |
| why must we consider the wave properties of an electron but not the wave properties of macroscopic objects? | the wavelength of the electron is similar in size to the atom and affects its properties, whereas the wavelength of the macroscopic objects is much smaller than the object and does not affect its properties. |
| what is the difference between the valence electrons of two elements in the same column? | the valence electrons have different energies, and they are in different size orbitals |
| K+ and Cl- have the same electron configuration, but why does Cl- have a larger atomic radius? | Cl- is larger because fewer protons are attracting the same number of electrons as in K+ |
| if given a table of ionization energies, how do you determine what element it is? | by when the ionization "jumps" (increases a large amount) is when it goes from valence electrons to core electrons |
| atomic radius decreases from left to right across a row on the periodic table because? | the relative attraction between the protons and the outer electrons increases. |
| example: an elements electron configuration is - [Kr] 5s^2 4d^10 5p^5. How many valence electrons does it have? | 7 because valence electrons are in the outermost orbital so only the "5" orbitals contain valence electrons not the 4 in this case. |
| nuclear reactions can release large amounts of energy because? | part of the mass of the reactants is converted into energy |
| what happens at the atomic level to produce a line on an emission spectrum? | when an electron transitions from a higher energy level to a lower energy level it emits a photon |
| why are emission lines different for each element? | each element has a specific energy, since the difference in energy between those levels are different, the energies of the photons released will also be different, different energy photons have different colors |
| if a spectrum was taken on the emissions from a star 300 light years away that contained Hg, would it look the same of different? | the lines would have the same pattern but would be slightly red shifted because of the Doppler Effect |
| what element most likely gives rise to the absorption spectrum? | hydrogen the lines are in the same place in absorption and emission spectra. this occurs because the photons that are absorbed and emitted have the same energies and wavelengths. this is because the energy difference between the energy levels is same. |
| what are the aspects of atomic structure that determine the electrostatic forces that control the size of an atom? | ENC shell/principal quantum number of valence electron |
| how do we support the idea that electron energies are quantized? | IEs are constant and replicable for any given electron means that this amount of energy must be added to the atom to eject the electron |
| which property of electromagnetic radiation can be explained with the double slit experiment? | the interference of light, when a beam of light passes through two small slits the two resulting waves interfere with each other |
| if the intensity of green light is increased what changes? | the amplitude of the wave, and the number of photons emitted |
| which experimental parameter could you increase to cause electrons to be ejected from the metal? | the frequency of the light, currently the photons don't have enough energy to overcome the attractive interaction and increasing the frequency would increase the energy of each photon |
| on an energy diagram absorption is represented by an __________ arrow. | upward |
| why are the absorption spectra different for neon and argon? | the differences in energy between energy levels are not the same for neon and argon |
| why must we consider the wave-like properties of an electron but not a larger object? | the wavelength of an electron is similar in size to the electron and therefore affects the properties of the electron |
| would S^2- or Ca^2+ have a smaller ionic radius? | Ca^2+ is smaller because it has more protons pulling on the same number of electrons as in S^2- |
| where would you predict there to be a big jump in the successive ionization energies for oxygen? | between IE 6 and IE 7 because it requires more energy to remove a core electron than to remove a valence electron |
| what evidence supports the claim that all matter and energy in the universe were once concentrated in a single point? | the absorption spectra of galaxies are red shifted because those galaxies are moving away from us |
| when a covalent bond is formed between two hydrogen atoms energy is ________ and a ________ is formed | released, molecule |
| what is an example of nuclear fusion? | two H + one H ----> three He |
| consider the potential energy diagram for two nuclei as they approach each other, when the nuclei are separated by a large distance the potential energy ________, the nuclei ________ each other due to electrostatic interactions. | decreases, repel |
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