G-Chemistry (10) Test 2 Review (PDF)

G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 Atomic Structure Materials: Slides Unit 3: Early History (all) Unit 4: Quantum Model (slides 1-20) Student packets Unit 3 packet...

G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 Atomic Structure Materials: Slides Unit 3: Early History (all) Unit 4: Quantum Model (slides 1-20) Student packets Unit 3 packet Unit 4 Packet Textbook CK-12 Chapter 3: Atomic Structure CK-12 Chapter 4: Electrons If it is on my slides - you need to know it. On the test, you will be provided with the Periodic Table containing symbols, names and average atomic weights of the elements (see last page). Recommended videos: Unit 3 videos: Understanding Atomic Number and Atomic Mass Protons, Neutrons, Electrons and Mass Number Isotopes Elements vs. Atoms How to Calculate Atomic Mass Practice Problems The Periodic Table Explained Unit 4 videos: Emission Spectra and the Bohr ModelBohr’s atomic model A Better Way To Picture Atoms How Small is the Atom You should be able to: UNIT 3: EARLY ATOMIC MODELS Know the basics of Democritus and Aristotle’s ideas: Democritus: ○ He created the atomic theory which stated, matter is made up of empty space through which atom’s move. Atoms are tiny indestructible objects, and lastly different atoms have different sizes and shapes, Plato's addition: these shapes are geometric solids.  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 Aristotle: ○ He created the essence theory, which states that matter is indefinitely continuous and is made up of four elements which are, earth, fire, water, and air (wind). Also, all matter has a fundamental essence that gives it its properties. Understand the Law of Conservation of Matter: Law of Conservation of Matter: ○ This was created by Lavosier and states that mass is neither created nor destroyed during chemical reactions or physical changes. Also, the total mass before the reactions, will be equal to the total mass after the reaction. Finally, this was very revolutionary because if you burn wood, the ashes weigh less than the wood that was originally burned. Understand the postulates of Dalton’s Atomic Theory, know which postulates still apply and which are no longer true: Dalton’s atomic theory facts which are true: ○ Atoms of different elements have different properties- true ○ Matter cannot be broken by chemical means- true ○ Atoms obey the law of conservation of mass – the weight of what we make is equal to the weight of what we started with-true ○ Atoms obey the law of multiple proportions (known as Dalton’s law)- true. It leads to the far more important understanding that atoms always combine in whole number ratios to form chemical compounds (i.e. H2O, never H2.1O0.8 ). Dalton’s atomic theory facts that are false: ○ All matter is made of small, indestructible particles called atoms. False: Atoms can be broken. A better statement that’s still true: Matter cannot be broken by chemical means. ○ Atoms of the same element have identical properties. False: The presence of isotopes (atoms with different masses) disproves this. Explain J.J. Thomson’s experiment, his results and his conclusions: J.J. Thomson’s experiment: ○ In 1987, Thomson did an experiment and concluded that very small negative particles called “electrons” existed in 1987. Explain J.J. Thomson’s Plum Pudding Model Plum Pudding Model:  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 ○ Thomson also concluded the following, because atoms are electrically neutral, they must contain a positive charge to balance the negative electrons. Also, because of electrons having so much less mass than atoms, atoms must contain other particles that account for most of their mass. Explain Rutherford’s Gold Foil Experiment, results and conclusions: Gold Foil Experiment results: ○ Though most of the particles traveled straight through the foil, others went bouncing off at crazy angles. The alpha particles would only be deflected when they passed near the small positively charged nucleus of an atom, because like charges repel one another. Gold Foil Experiment conclusions: ○ Most of the atom is empty space, the majority of the mass and all the positive charge is concentrated in the middle of the atom. Also, the negatively charged electrons float around throughout the rest of the atom’s empty space. Contrast J.J. Thomson’s Plum Pudding Model with Rutherford’s nuclear model: Distinguish between protons, neutrons and electrons. Compare their charges, masses, functions and locations in the atom: Protons: ○ Protons were observed by Eugen Goldstein and they were identified and named by Ernest Rutherford. Protons have the same charge as electrons, but they are opposite in sign (+). Protons are 1837 times heavier than  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 electrons. Protons are located in the nucleus of an atom, which is small. Most of the mass of an atom is due to the nucleus. The number of protons always determines the atom’s identity. Positive protons repel each other making the nucleus unstable. Neutrons: ○ Neutrons were postulated to exist in a nucleus in the 1920’s, but only in the year 1932, James Chadwick was able to demonstrate and prove their existence. Neutrons weigh almost the same mass as protons. Neutrons are also located in the nucleus of an atom. Neutrons are present to stabilize the protons. Neutrons have a neutral charge. Electrons: ○ Electrons are located outside of the nucleus. Most of the volume of the atom is due to the electrons. Electrons orbit surrounding the nucleus, and were discovered by J.J Thomson. Electrons have a negative charge. Calculate number of protons, neutrons, and electrons using periodic table and given mass number: Atomic Number: ○ The number of protons that are present in an atom, found on the periodic table. Mass Number: ○ Sum of the number of protons + neutrons, not found on the periodic table. Atomic mass: ○ Decimal number, found on the periodic table. Understand what isotopes are and how to write/draw their symbols and names: Isotopes: ○ Atoms of the same element have different charges. They have the same number of protons, so they have the same atomic number, but they contain different numbers of neutrons, so they have different mass numbers. Symbols: 12 13 14 ○ C ,C ,C Calculate the average atomic mass of an element given the natural abundances of its isotopes: Atomic mass: ○ Average atomic mass is found using all the isotopes of an element weighted by their natural abundances. Natural abundances:  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 ○ The percent occurrence of isotopes of a chemical element as naturally found on a planet. How to calculate average atomic mass: (mass of isotope 1) X (abundance of isotope 1) + (mass of isotope 2) X (abundance of isotope 2) = average atomic mass Example: Rubidium has two common isotopes, 85Rb and 87Rb. If the abundance of 85Rb is 72.17% and the abundance of 87Rb is 27.83%, what is the average atomic mass of rubidium? Answer: 72.17% 85 27.83% 87 100% = 0.7217 Rb 100% = 0.2783 Rb (0.7217 X 85.00 amu) + (0.2783 X 87.00 amu) = 85.56 Know how the periodic table is organized: be able to identify group and period numbers: Atomic Number: ○ Elements are arranged in order of atomic number, which is written at the top of the box. Atomic weight: ○ The atomic weight of an element appears at the bottom of the box. Periods: ○ Periods are horizontal rows of elements Group Numbers: ○ Elements are arranged by similar properties in vertical columns called groups. Numbers 1-18, are used for the columns from left to right. The letter A, is used for the representative elements 1A to 8A and the letter B, is for the transition elements. The transition metals are: 1a- Alkali Metals 2a- Alkaline earth metals 7a (17)- Halogenous 8a (18)- Noble gases (The only two liquid elements at room temperature are Bromine and Mercury.) Blue elements are gases UNIT 4: QUANTUM MODEL Know what electromagnetic radiation is and be able to give examples: Electromagnetic radiation: ○ Light is how we refer to electromagnetic radiation  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 ○ In a generic sense, electromagnetic radiation applies to light we can see, infrared light. UV light, microwaves, radio waves, X-rays. Understand the difference between continuous and the line spectra: Continuous spectrum: ○ This is when the solar spectrum, or white light looks like a pretty rainbow when you use a prism to break apart the colors, and you can see all the colors with no breaks in between. Line spectra: ○ The phenomenon of line spectra is observed when an electron absorbs energy (for example, from heat or electricity) and jumps from a lower energy level to a higher one. This process is called excitation. However, the electron cannot stay in the higher energy level forever. Eventually, it will fall back to its original lower energy level, and when it does, it releases energy in the form of light. The energy released corresponds to a specific wavelength of light, and because only certain energy levels are allowed, only certain wavelengths (or colors) of light are emitted. This is why, instead of a continuous rainbow of colors, we see a line spectrum—distinct lines of color, each representing a specific energy change. Each element has its own unique set of energy levels, so when electrons move between these levels, they produce a unique line spectrum, acting like a fingerprint for that element. Bohr’s model helps explain why we see specific lines of light rather than a full spectrum. Be able to explain Bohr’s planetary model: Bohr's Planetary Model (1920’s): ○ All of the positive charge and mass of the atom is in the nucleus, which is tiny and heavy, like the sun (same idea as Rutherford) ○ The electrons circle the nucleus in circular orbits (like planets around the sun) ○ The orbits are numbered with variable n (from 1 to infinity) ○ The closer to the nucleus the orbits are, they have the lowest amount of energy, but the farther away the orbits are, they gain the most amount of energy. ○ The variable n is used in Bohr’s equations to determine, both the distance of the orbits from the nucleus, and their energies. ○ When an atom is at rest, each electrons lies in its lowest possible energy orbits called ground state ○ When energy is added, the electrons absorb it, and jump to the higher energy orbits, called excited states  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 ○ After time has passed, the electrons fall back down to their original ground state orbits, giving off the energy they absorbed, in the form of light (photon) ○ This precise energy corresponds to one line in the line spectrum Understand what happens during electron transitions up and/or down the levels: Transitioning between ground state and excited state: ○ When an atom is at rest, each electrons lies in its lowest possible energy orbits called ground state ○ When energy is added, the electrons absorb it, and jump to the higher energy orbits, called excited states ○ After time has passed, the electrons fall back down to their original ground state orbits, giving off the energy they absorbed, in the form of light (photon) Understand the connection between energy (light) and electrons: Connection between light and electrons: ○ Different gasses emit light of different characteristics of colors when an electric current is passed through them, and these colors can be used to identify an element, by a process called spectroscopy. Practice problems: 1. Who made the discovery that cathode rays were actually negatively charged particles called electrons? a) Thomson b) Bohr c) Rutherford d) Dalton 2. In a glass tube, electrical current passes from the negative electrode, called the ______ to the other electrode. a) cathode b) anode c) electron d) millikan 3. Whose model of the atom could be represented by a solid, indivisible sphere with a characteristic mass? a) Dalton b) Thomson c) Rutherford d) Bohr 4. Whose model of the atom could be represented by a positively charged cloud with electrons distributed through it? a) Dalton b) Thomson c) Rutherford d) Bohr 5. The nucleus of the atom was discovered by a) Thomson b) Bohr c) Rutherford d) Dalton  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 6. In Rutherford's experiments, most of the alpha particles aimed at gold foil a) bounced back. c) were absorbed by the foil. b) passed through the foil. d) combined with the foil. 7. Because most particles fired at metal foil passed straight through, Rutherford concluded: a) atoms were mostly empty space c) electrons formed the nucleus b) atoms contained no charged particles d) atoms were indivisible 8. Because a few positively charged particles bounced back from the foil, Rutherford concluded that such particles were a) striking electrons b) indivisible c) repelled by densely packed regions of positive charge d) magnetic. 9. Rutherford's experiments led to the discovery of the a) electron b) nucleus c) cathode ray d) neutron. 10. Rutherford's experimental results led him to conclude that atoms contain massive central regions that have a) a positive charge b) a negative charge c) no charge d) both protons and electrons. 11. Name the group and period number for the following elements: a) Sulfur (atomic number 16) b) Vanadium (atomic number 23) c) Platinum (atomic number 78) 15. Protons, neutrons, and electrons are examples of ________. A) elements C) compounds B) ions D) subatomic particles 16. The lightest of the subatomic particles is the ________. A) neutron D) proton B) electron E) atom C) nucleus 17. Which of the following is true about the proton? A) It has a charge of -1 and is in the nucleus of the atom. B) It has a charge of +1 and is in the nucleus of the atom. C) It has a charge of 0 and is in the nucleus of the atom. D) It has a charge of -1 and is not in the nucleus of the atom. E) It has a charge of +1 and is not in the nucleus of the atom. 18. The number of neutrons in an atom is equal to the ________.  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 A) atomic number D) mass number - the atomic number B) mass number E) number of protons C) mass number + the atomic number 19. The correct symbol for a uranium atom with a mass number of 235 is ________. A) U D) U B) U E) Ur C) Ur 20. Consider a neutral atom with 30 protons and 34 neutrons. The atomic number of the element is ________. A) 30 C) 34 B) 32 D) 64 21. How many protons are in an isotope of sodium with a mass number of 25? A) 11 C) 15 B) 14 D) 25 22. The element boron occurs in nature as two isotopes: Boron-10 has a mass of 10.0130 amu and its abundance is 19.9%. Boron-11 has a mass of 11.0093 amu and its abundance is 80.10%. From these data, calculate the average atomic mass of the element boron. 23. A fictional element, Eternium (Et), has three naturally occurring isotopes: Eternium-210, Eternium-215, and Eternium-220. In a sample of Eternium, 50% is Eternium-210, 20% is Eternium-215, and the remainder is Eternium-220. Calculate the average atomic mass of Eternium. 24. Show two ways to represent the isotope for an element containing 20 protons and 22 neutrons. Use the correct symbol and the hyphenated name of the element. 25. Which one of the following is considered to be dangerous/harmful radiation? A) visible light D) microwaves B) radio waves E) infrared radiation C) X-rays 26. In Bohr’s model, what makes electrons jump to higher energy levels? What happens to electrons after it? 27. Complete the table below using the periodic table:  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 Element Symbol Atomic # Mass # Protons Neutrons Electrons 7 Lithium 3Li 3 4 3 12 Carbon 6 C 12 6 6 Sodium 12 207 82 Pb 125 48 22 Ti 48 66 30 Zn 80 122 37 17 Tungsten 74 184 28. According to the periodic table, the number of electrons in Carbon-14 is (a) 12 (b) 12.011 (c)14 (d) 6 29. Evidence that electrons exist in distinct energy levels outside the nucleus is provided by a. cathode rays c. atomic masses b. spectral lines d. radioactivity 30. How many protons, neutrons and electrons are in Uranium-238? Write the isotope symbol for Uranium-238. It’s atomic number is 92. 31. Bohr’s theory support’s which of the following statements? a. atoms are mostly composed of empty space b. electrons orbit the nucleus of an atom at distinct energy levels c. atoms are neutral d. All of the above are true 32. The specific wavelengths of light seen through a prism that are made when high voltage current is passed through a tube of hydrogen gas is called a. Line spectrum emission b. Electron configuration c. Quantum effect d. Continuous emission spectrum 33. How does the Bohr model explain the appearance of an emission spectrum for hydrogen? What type of spectrum is observed?  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 Answers to practice problems: 1. a 2. a 3. b 4. c 5. d 6. a 7. b 8. c 9. b 10. a 11. c 12. b 13. A 14. a) group 16, period 3 b) group 5, period 4 c) group 10, period 6 15. D 16. B 17. B 18. D 19. D 20. A 21. A 22. (10.0130)(0.1990) + (11.0093)(0.8010)= =10.811 amu 23. 214 amu 42 24. 20Ca and Calcium - 42 25. C 26. Absorption of energy from light or heat makes electrons jump to higher energy levels. After a while, electrons relax, release all that energy back and jump down to their ground energy level. 27. Complete the table below using the periodic table: Element Symbol Atomic # Mass # Protons Neutrons Electrons 7 Lithium Li 3 3 7 3 4 3  G-Chemistry (10) Test 2 Review Dr. Gimpelev’ 24 12 Carbon C 6 6 12 6 6 6 23 Sodium 11 Na 11 23 11 12 11 207 Lead 82 Pb 82 207 82 125 82 48 Titanium 22 Ti 22 48 22 26 22 66 Zinc 30 Zn 30 66 30 36 30 Mercury Hg 80 202 80 122 80 37 Chlorine 17 Cl 17 37 17 20 17 184 Tungsten 74 W 74 184 74 110 74 28. d 29. b 30. Uranium-238 has 92 protons based on the periodic table, 92 electrons and 146 neutrons. 238 U 92 31. d 32. a 33. When hydrogen atoms are excited or absorb the right amount of energy, the electrons jump up to certain energy levels. When they fall back down, they release energy and a line spectrum is created.