CH 301 Unit 1 Exam 1 Review Notes PDF

CH 301 Unit 1 Exam 1 Review Notes 1. EMR Ranking & Calculation Here are the skills and knowledge you need to know to answer this question on the exam: One question will be a plug and chug calculation. You will be given all needed...

CH 301 Unit 1 Exam 1 Review Notes 1. EMR Ranking & Calculation Here are the skills and knowledge you need to know to answer this question on the exam: One question will be a plug and chug calculation. You will be given all needed equations and constants, but no calculators. One question requires that you are able to rank electromagnetic radiation Cosmic rays ! #! 𝐸 = ℎ𝜐 𝜈=" 𝐸= " ( Radio Micro Infrared Visible UV X-rays Gamma- ℎ = 6.6 𝑥 10$%& 𝐽𝑠 𝑐 = 3 𝑥 10' ) Waves Waves rays You will be asked to find Energy (E) when wavelength (l) and frequency (v) given a starting value Increasing E and ν 1. Make sure you turn wavelengths into meters. *Know your metric Increasing λ conversions* Also have a general feel for wavelength values: 2. Be able to do simple scientific notation math *Know conversions to meters* 3. The numbers will correspond to simplifications. That will make math easy to Visible = 300 to 500 nm UV = 300 to 10 nm don’t panic. 4. Note the example below. Typical of exam. Note how math simplifies. IR = 800 nm to 1 µm X-rays =.01 to 10 nm Practice exam problem: Practice exam problem: If a photon’s wavelength is 663 nm, what is its energy? What is the correct order of increasing energy? 1. 4.40 x 10-37 J 1. Microwaves, visible light, UV light, x-rays, gamma rays correct Ranking leading to 2. 3.00 x 10-22 J 2. Microwaves, x-rays, gamma rays, visible light, UV light dumb mistakes!! 3. 4.40 x 10-40 J 3. Microwaves, UV light, visible light, x-rays, gamma rays Be careful about 4. 3.00 x 10-19 J correct 4. X-rays, gamma rays, microwaves, visible light, UV light most to least vs. #! 5. UV light, visible light microwaves, x-rays, gamma rays least to most Explanation: 𝐸= " READ CAREFULLY 𝑚 1 10* 𝑛𝑚 Explanation: = 6.63𝑥10$%& 𝐽𝑠 3.0𝑥10' 𝑥 𝑠 663 𝑛𝑚 1𝑚 Microwaves < visible light < UV light < x-rays < gamma rays = 3𝑥10$+* 𝐽  CH 301 Unit 1 Exam 1 Review Notes 2. Interactions between light & matter Here are the skills and knowledge you need to know to answer this question on the exam: Cosmic rays These are two simple knowledge-based problems. Everyone should get those by learning what is on this page. Radio Waves Micro Waves Infrared Visible UV X-rays Gamma-rays 1 mm to 100s m 100 𝜇m 100 cm 800 to 1000 nm (1 𝜇m) 300 – 800 nm 300 to 10 nm 10 to 0.01 nm < 0.01 nm Spin nucleus Excited spin of Causes vibrations Causes excited Excites Excites core e- Associated with excited used in electrons. in molecules. value of e-’s to valence ’s in atoms. decay of atom MRI (non-invasive). Excites rotation of Used in night higher energy electron. Used in nucleus. Responsible for 𝐻, 𝑂, fats molecules vision goggles. level. Lyman series medicine for Are emitted from AM, FM radio. around 12 cm to Excited wavelength Solution for H for H emission invasive in stars hence comic cook food. of –OH in ethanol atom. n = 1 excited. imaging. ray name. and used to This is rays of Causes sun Cause cell measure detection for burn. mutations so intoxication. human eye. limit exposure. Practice exam problem: You will know this Practice exam problem: When a given molecule absorbs a photon of infrared (IR) radiation material if you can repeat Radiofrency radiation has what kind of impact on matter? 1. It begins to vibrate. correct it our loud or write it 1. It makes electrons spin. 2. It promotes electrons into delocalized bonding orbitals. down. You aren’t sure you 2. It makes the molecule rotate. 3. It bring to rotate. will get question right if 3. It makes the nucleus split. 4. Its electrons are excited to higher energy levels. you can’t say the 2 to 3 4. It makes the nuclei spin. correct 5. It leads to hemolytic cleavage. bullets for each.  CH 301 Unit 1 Exam 1 Review Notes 3. Failures of classical mechanisms (photoelectric effect) Here are the skills and knowledge you need to know to answer this question on the exam: Be able to explain the photoelectric effect. According to classical mechanics, the intensity of the light should make any Lo Hi e- w gh e- ℎ𝜐 energy eject electrons. But this does not happen. Classical mechanics fails. 𝐸 𝐸 (ℎ g (ℎ e- According to Plank and Einstein, thinking of light as a particle 𝜐) hin 𝐸-./)#012 𝜐) t 𝐸 = ℎ𝜐 ← a photon no of enough energy will eject electrons. Metals with low Active metal surface Equation: ionization energy 𝐸 = ℎ𝜐 = 𝐸-./)#012 + 𝐾. 𝐸. like alkali metals. photon If you can’t talk this page out loud, you Photons above threshold cause electrons will get this question to be ejected with higher velocities. wrong. Practice exam problem: Which of the following statement(s) is/are true about the photoelectric effect? I) The sum of the work function and kinetic energy of an ejected electron is proportional to the frequency of incident light. II) Given light of high enough intensity, electrons can be ejected from any surface. III) Einstein employed the concept that photons have quantized amounts of energy to explain the effect. This is a theory question, you 1. I, II Explanation: Classical mechanisms predicted that light of any wavelength could be need to own the words to get 2. I, II, III able to eject electron from a metal surface it was sufficiently intense, which was this right. 4 or 5 statement 3. I only inconsistent with the observed threshold. This threshold effect, the ejection energy, will be either T or F> Be sure 4. II, III required that light energy was quantized. Conservation of energy lets us conclude to distinguish T from F. 5. I, III correct that 𝐾𝐸 = ℎ𝜈 − 𝜙  CH 301 Unit 1 Exam 1 Review Notes 4. Wave particle duality of light and matter Here are the skills and knowledge you need to know to answer this question on the exam: Another theory question. Lots of words. Your multiple-choice problem will have several statements. Some true and some false. Pick out which is which. Talk this page out loud and make sure you own all the vocabulary. If you get stuck, you don’t know it!!! Light is a wave and a particle Matter is also a wave and a particle § Light used to be thought of as wave-like, in keeping with classical § Matter is a particle. It behaves according to Newtonian physics. mechanics. Wave phenomena includes: diffraction, reflection, § But as matter gets smaller, it does not behave like particle. Can’t assign polarization, etc. trajectories to electrons. § Downfall of classical mechanics: Blackbody radiators, H emission § deBroglie postulated that matter also acts as a wave. spectra and photoelectric effect can’t be explained by classical § This is shown in the Davisson and Germer experiment where mechanics. electrons have a diffraction pattern. § Light as a particle 𝐸 ≡ ℎ𝑣 ≡ 𝑝ℎ𝑜𝑡𝑜𝑛 is postulated. e- diffraction Practice exam problem: The famous electron diffraction pattern is proof of what concept? 1. Particles can exhibit wave-like properties. correct 2. The location and trajectory of electrons can be found. “light and matter both have dual nature: 3. Electromagnetic radiation can exhibit wave-like properties. wave-like and particle-like.” 4. Electrons can spin when hit by microwave radiation.  CH 301 Unit 1 Exam 1 Review Notes 5. de Broglie theory Here are the skills and knowledge you need to know to answer this question on the exam: Be able to interpret the de Broglie wave equation. Plank’s constant wavelength ℎ 𝑚𝑣 = 𝑚𝑜𝑚𝑒𝑛𝑡𝑢𝑚 of 𝜆= matter 𝑚𝑣 Mass of Particle Velocity of Particle § Note inverse relationship between wavelength and wave. The larger the wave, the smaller the wavelength. § Because ℎ = 6.6×10$%& 𝐽𝑠 is so small, this says that large particle that you can see have undetectably small wavelengths. Simple estimate is 100 kg person walking 1 𝑚/𝑠 ≡ 10$%3 𝑚 wavelength. § But electrons and protons are small enough that their wavelength can be measured!! An e- has 𝜆 of nanometers, about the length of an atom. Protons are 10% layer so they have a 𝜆 of picometers depending on velocity. Practice exam problem: According to de Broglie, which of the following objects has the smallest wavelength? ** This is why quantum mechanics 1. electrons Is needed. It explains wave behavior of 2. neutrons electrons ≡ where they are. ** 3. protons 4. molecules correct  CH 301 Unit 1 Exam 1 Review Notes 6. Rydberg equation calculation Here are the skills and knowledge you need to know to answer this question on the exam: Be able to understand and manipulate: I love the Rydberg equation. It ties experiment and theory to explain the behavior of 1 1 electrons in an H atom. Bohr’s atom, that you learned in elementary school, is the bridge 𝑣=𝑅,− , between experiment and theory. 𝑛1 𝑛# 𝑣 ≡ 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 𝑏𝑢𝑡 𝑒𝑎𝑠𝑖𝑙𝑦 𝑐𝑜𝑛𝑣𝑒𝑟𝑡 𝑡𝑜 𝐸, 𝜆 𝑅 ≡ 𝑅𝑦𝑑𝑏𝑒𝑟𝑔 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡, 𝑖𝑠 𝑎𝑙𝑠𝑜 𝑖𝑜𝑛𝑖𝑧𝑎𝑡𝑖𝑜𝑛 𝑒𝑛𝑒𝑟𝑔𝑦 𝑜𝑓 𝐻 𝑎𝑡𝑜𝑚 3.3×10+4 𝐻𝑧 Note that as energy spectra get 𝑛1 ≡ 𝑙𝑜𝑤𝑒𝑟 𝑒𝑛𝑒𝑟𝑔𝑦 𝑙𝑒𝑣𝑒𝑙 ! 𝑛# ≡ 𝑢𝑝𝑝𝑒𝑟 𝑒𝑛𝑒𝑟𝑔𝑦 𝑙𝑒𝑣𝑒𝑙 closer they become ! function: Bohr’s Atom + " ! ! ! e- , !# "# ## , or 1, 0.25, 0.11 Practice exam problem: Which of the following emission lines corresponds to part of the Balmer series of lines in the spectrum of a hydrogen atom? Fall to UV n = 1 (Lyman series) I) n = 2 à n = 1 II) n = 4 à n = 2 Practice exam problem: Fall to visible n = 2 III) n = 4 à n = 1 For a Bohr atom, which of the following transitions (Balmer series) **Be able to IV) n = 3 à n = 2 emits the highest energy photon? + V) n = 4 à n = 3 rank relative 1. From n = 10 n = 8 Fall to IR n = 3 energies for 2. From n = 4 to n = 3. (Paschen series) different 1. II and III only 3. From n = 6 to n = 5 2. II and IV only correct transitions** 4. From n = 2 to n = 1 correct 3. V only Explanation: The change in energy decreases between This is what makes emission spectra Balmer the same 4. I and III only energy levels as they get closer together and move 5. II, III, and IV only away from the nucleus, so the two energy levels with Explanation: The Balmer series is produced by electronic transitions the largest difference in energy will be the two lowest Note discrete not which either begin (absorption spectra) or end ( emission spectra) at energy levels in the list. continuous ! the energy level n = 2. These correspond mostly to the visible region. Reflects "!  CH 301 Unit 1 Exam 1 Review Notes 7. Quantum mechanics application – H atom Practice exam problem: Here are the skills and knowledge you need to know to answer this question on the exam: The size of an atomic orbital is determined by which quantum number? More theory. Be able to explain and distinguish T/F questions. 1. 𝑚1 Schrodinger developed quantum mechanics. Explains wave behavior of electrons. 2. 𝑙 Cannot know exact location but can know most probable location. 3. 𝑚) Not all locations are possible. There are rules for where electrons are found. There are quantum rules 4. n correct n U energy level, distance from nucleus, n = 1, 2, 3,... (like Ruberg) ≡ shell 𝑙 U shape of energy level, 𝑙 = 0, 1, 2,... n – 1 → s shape: p shape: d shape s p d spherical The shading id most likely 𝑚1 U orientation of shape, 𝑚1 = −𝑙,... , 0,... , +𝑙 location of electrons so s has 1 orientation: 0 p has 3 orientations: -1, 0, +1 y y y x x x z z z d has five orientations: -2, -1, 0, +1, +2 * Note. All of this translates to periodic table so don’t 𝑚) U electron spin need to memorize. But remember: 𝑛 = 𝑠ℎ𝑒𝑙𝑙 1, 2, 3 , 𝑙 = 𝑠𝑢𝑏𝑠ℎ𝑒𝑙𝑙 𝑠, 𝑝, 𝑑 , 𝑚1 = 1 1 𝑜𝑟𝑏𝑖𝑡𝑎𝑙 # 𝑙𝑖𝑘𝑒 𝑠𝑝 𝑜𝑟 3𝑠 (2 𝑒 $𝑝𝑒𝑟 𝑜𝑟𝑏𝑖𝑡𝑎𝑙)* ≡ 𝑚) = + vs ≡ 𝑚) = − 2 2  CH 301 Unit 1 Exam 1 Review Notes 8. Quantum numbers boundary Here are the skills and knowledge you need to know to answer this question on the exam: Correns boundary condition on particles page, applies to multiple electron Another type of question asks whether 4 quantum numbers system to explain how many possible electrons fit the condition. are allowed for an e-. n = 1, 2, 3,... Example: How many electrons in n = 1 shell? Example: n = 1, 𝑙 = 1, 𝑚1 = 1, 𝑚) = + , + 𝑙 = 0, 1, 2,... n – 1 Only 2. Why? n = 1 so 𝑙 = 0 only so 𝑚1 = 0 only since NO - 𝑙 can only be 0 when n = 1 (𝑙 = n – 1) 𝑚1 = −𝑙,... , 0,... , +𝑙 + + + + + 𝑚) = + , , − ,, 2 e- in n = n shell Example: n = 4, 𝑙 = 2, 𝑚1 = -2, 𝑚) = + , 𝑚) = + , , − , Example: How many electrons in n = 1 though 3 are p? Yes! Answer is 12. Why? n = 1 has no p orbits, n = 2 has 3 p- + Example: n = 3, 𝑙 = 2, 𝑚1 = -3, 𝑚) = − , orbitals x2 = 6 e-, n = 3 has 3 p-orbitals x 2 = 6 e- → 12 e- total You will have one question like this NO - 𝑚1 = −𝑙,... , 0,... , +𝑙 You will have one question like this Practice exam problem: Practice exam problem: Pay close attention to the In an atom, what would be the maximum number of Which set of quantum numbers does NOT provide a patterns of the wave equation electrons having the quantum numbers n = 6 and 𝑙 = 2? satisfactory solution to the wave equation? and try to visualize the shape, 1. 72 1. n = 2, 𝑙 = 0, 𝑚1 = -1 correct orientation, and spin. 2. 6 2. n = 1, 𝑙 = 0, 𝑚1 = 0 3. 5 3. n = 4, 𝑙 = 2, 𝑚1 = +2 4. 10 correct 4. n = 5, 𝑙 = 3, 𝑚1 = -3 5. 8 5. n = 3, 𝑙 = 2, 𝑚1 = -1  CH 301 Unit 1 Exam 1 Review Notes 9. Periodic table nomenclature Here are the skills and knowledge you need to know to answer this question on the exam: You will always have a periodic table on the exam. It tells you so much if you know how Practice Exam Problem! to read it. It lets you calculate molar mass Fill in the blanks: potassium is one of the most It lets you know the numbers of electrons, protons, and neutrons well-known elements in the alkali metal ____. It It tells you the number of valence electrons is in the ____ which makes it a ____ element. Its It answers quantum rules about 𝑛. 𝑙. 𝑚1 , 𝑚) single valence electron is in the ____ subshell of It tells you the energy levels of electronic configurations the ____ shell, making it very reactive. It reacts It tells you the state of element form readily with non-metals to form ____. 1. series; s block; common; l = 1; n = 4; networks What else? Know the definitions of: 2. row; d block; main group; l = 1; n = 4; salts Period, group, family, block, main group, transition metal, lanthanum, actinium series, 3. family; s block; main group; l = 0; n = 4; salts alkali metal, alkali earth metals, halogens, noble gases, shell, subshell, orbital, non- 4. row; d block; non-metal; l = 1; n = 3; alloys metals, metals, metalloids. 5. family; s block; reactive; l = 0; n = 3; alloys Answer: 3.  CH 301 Unit 1 Exam 1 Review Notes 10. Aufbau, Hund, Pauli theory You will be given examples of orbital diagrams and must discern if it is Here are the skills and knowledge you need to answer this question correctly on the exam: correct or wrong. In addition to knowing quantum rules for n, l, ml, ms when filling electron configuration for multiple electron, there are also rules for how they fill. Aufbau: Pauli: Electrons fill from the lowest to No 2 electrons have the same Practice Exam Problem! the highest. set of quantum numbers. Which of the following violates 3p ↑ ↑ This translates as ”no more Aufbau? 3p ↑ ↑ ↑ 3s ↑↓ than 2 e- per orbital” 3s ↑ Yes! 2p ↑↓ ↑↓ ↑↓ 2s ↑↓ 2p ↑↓ ↑↓ ↑↓ 2s ↑↓ 1. 1s ↑↓ 2s ↑↓ No! We need to fill 3p ↑ ↑ ↑ No! You can’t 1s ↑↓ 1s ↑↓ the 3s before we fill 3s ↑↓↑ have 3 the 3p. 2p ↑↓ ↑↓ ↑↓ 2p ↑↓ ↑↓ ↑↓ electrons in an 2s ↑ 2s ↑↓ orbital. Hund: 1s ↑↓ 2. 1s ↑↓ Spread out electrons when they have the same energy 3p ↑↓ ↑ ↑ 2s ↑↓ 3p ↑ ↑ ↑ 3s ↑↓ 3. 1s ↑↓ levels in p and d orbitals 3s ↑↓ Remember the quantum 2p ↑↓ ↑↓ ↑↓ Yes! 2p ↑↓ ↑↓ ↑↓ number ms: which only has 2s ↑↓ 3p ↑↓ ↑ two numbers that it could be 4. 1s ↑↓ 2s ↑↓ 1s ↑↓ 3s ↑↓ $! &! 1s ↑↓ , 𝑎𝑛𝑑. 2p ↑↓ ↑↓ ↑↓ % % Answer: 2. 2s ↑↓ Yes! No! the electrons 1s ↑↓ aren’t spread out.