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Ch4.1 – Atomic Structure History of the atom Aristotle- Everything is made of a substance called “hyle.” Re-arrange hyle to make different substances. Aristotle's philosophies accepted by Roman Catholic church - Western science in dark ages until ~ 1500’s. John Dalton (1800’s): Father of Atomic Theory. 1. Everything is made up of tiny, indestructible particles. He called them atoms. 2. Pictured atoms as tiny, solid spheres. 3. All atoms of the same element are identical atoms of different elements are different. 4. Atoms of different elements combine in whole number ratios. 5. Chemical reactions occur when atoms separate from each other, join with others, but the atoms themselves never change. J.J. Thompson (1897): Discovered the electron. Electrons have negative charge. Pictured atoms as a spheres with tiny, negative charges embedded throughout. Came up with the “plum pudding” model of the atom. Millikan (~1900) his oil drop experiment discovered mass/charge of electron. Ernest Ruthorford (1911): Discovered the nucleus of the atom in his famous “Gold Foil Experiment”. Nucleus is small, dense, positively-charged center of the atom. Electrons move around the nucleus. Niels Bohr (1913): Planetary model of atoms. Electrons move around nucleus in fixed orbits, based on energy levels, like planets around the sun. While not entirely accurate, his model is still often used today to provide visualization. Chadwick (1932): discovered neutron Subatomic particles Particle Symbol p+ Electron e– Neutron no Proton Charge Mass in grams Mass in amu +1 1.67x10-24 1 -1 9.11x10-28 1/1840 0 1.67x10-24 1 Protons and neutrons are located in the nucleus, are the same size, and contribute to mass. Electrons are located outside the nucleus, and are so small they don’t contribute to mass. Electron movement is the basis of chemistry! You MUST Remember the charge and location of EACH subatomic particle! Trivias 500,000,000,000,000,000,000,000,000,000,000 electrons equals 1pound 2,500,000,000,000 protons side by side = 1 inch Ex1) a) If an oxygen atom consists of a nucleus with eight protons and eight neutrons, what is the charge of that nucleus? b) If there are eight electrons surrounding that nucleus, what is the overall charge of this oxygen atom? c) What is the total mass of this atom in amus? Ch4 HW#1 Ch4 HW#1 1 – 4 1. Explain how Democritus came up with his theory every made of atoms: 2. Which statement would Dalton Agree with: a) Atoms are the smallest particles of matter. b) Mass of an iron atom is different from mass of a copper atom. c) Every atom of silver is Identical to every other atom of silver. d) A compound is composed of atoms of two or more different elements. 3. What did Rutherford’s gold foil experiment unexpectedly find? 4. a) If a fluorine atom consists of a nucleus with nine protons and nine neutrons, what is the charge of that nucleus? b) If there are nine electrons surrounding that nucleus, what is the overall charge of this fluorine atom? c) What is the total mass of this atom in amus? d) In nature, fluorine is always found with 10 electrons rather than nine surrounding its nucleus. What is the overall charge of this atom? Ch 4.2 - The Periodic Table 6 C Carbon 12.011 Atomic #: Mass #: 2 4 Ch 4.2 - The Periodic Table Atomic # Mass # 6 C Carbon 12.011 2 4 Electron Locations _p _n Atomic #: # of protons - the periodic table is arranged in increasing atomic #. - since all atoms are electrically neutral # protons = #of electrons Mass #: total mass of atom mass = protons and neutrons - do not count electrons → too small! Getting Subatomic Particles from the Periodic Table Mass # (prots & nuets) Ex1) 16 O 8 protons = Atomic # (prots) electrons = Neutrons = mass # – atomic # = neutrons = Ex2) 108 Ag 47 ____Protons, ____ electrons, ____ Neutrons Ex3) Sometimes written is this form : Carbon – 12 ____Protons, ____ electrons, ____ Neutrons Uranium – 238 ____Protons, ____ electrons, ____ Neutrons Isotope # HW#5) (copy to separate paper!) Element Potassium Symbol Atomic # # of protons 5 16 Y HW#6) Atomic # Mass # # Protons 9 #Electrons Symbol 10 14 47 55 Ch4 HW#2 5 - 8 # Neutrons 15 22 25 Ch4 HW#2 5 – 8 5) Element Potassium Symbol Atomic # # of protons 5 16 Y 6) Atomic # Mass # # Protons 9 # Neutrons #Electrons Symbol 10 14 47 55 15 22 25 7. An atom is identified as platinum- 195. a. What is the number 195 called? b. What is the symbol with #’s? 8. Determine the number of neutrons in each atom. a. carbon-13 b. nitrogen-15 c. radium-226 Ch4.3 Atomic Mass (Hand out periodic table) 1 Flourine atom has a mass of: 0.000 000 000 000 000 000 000 03155g What is that! How about in scientific notation: Ch4.3 Atomic Mass 1 Flourine atom has a mass of: 0.000 000 000 000 000 000 000 03155g What is that! How about in scientific notation: 3.155x10–23 g Looks better, but still not practical Ch4.3 Atomic Mass 1 Flourine atom has a mass of: 0.000 000 000 000 000 000 000 03155g What is that! How about in scientific notation: 3.155x10–23 g Looks better, but still not practical It was decided a smaller mass measurement is needed. mass of 1 proton = 1 atomic mass unit - since protons and neutrons are extremely close in mass, it was decided that 1 amu would be based on Carbon-12 With 6 protons and 6 neutrons, then ÷ by 12 nucleons = 1 amu Ch4 HW#3 9. Fill in the missing information, then draw Bohr models of the atoms, based on the electron locations listed on your periodic table. Element Symbol Mass Atomic Protons Neutrons # # Aluminum Al 27 Carbon 12 13 3 6 Chlorine 17 18 Chromium 24 28 Cobalt Copper 32 64 Gold 119 Helium 2 Hydrogen Iron 1 Period Group (Row) (Column) 0 30 13 Ch4 HW#3 9. Fill in the missing information, then draw Bohr models of the atoms, based on the electron locations listed on your periodic table. From P.T.: 2 Symbol 10 Al 3 13p 13 C Cl Cr Co Cu Au He H Fe Al Aluminum 27.0 14n Ch4 HW#3 9. Fill in the missing information, then draw Bohr models of the atoms, based on the electron locations listed on your periodic table. Symbol Al C Cl Cr Co Cu Au He H Fe Ch4.4 Isotopes and Average Atomic Mass Isotopes of the SAME ELEMENT obviously have the same # of protons, but differ in # of neutrons Ex1) Write the chemical symbol and find # of neutrons for: Carbon-12 and Carbon-13 Average Atomic Mass - each element can have many naturally occurring isotopes. The periodic table lists the mass of each element as an average based on the relative abundance of the isotopes. H – 1.0079 C – 12.011 - Cl – 35.435 - H – 1.0079 ( Over 99% of all hydrogen's are H – 1) ( A few are H – 2, or H – 3) C – 12.011 ( Almost all are C – 12) Cl – 35.435 - only 2 isotopes → Cl – 35 & Cl – 37 75% in nature are Cl – 35 25% are Cl – 37 So these are weighted averages Ex2) In nature, magnesium has three common isotopes. The 3 isotopes and their relative abundance are as follows: 79% is Mg-24 10% is Mg-25 11% is Mg-26 All of these are stable. Calculate the average atomic mass of Mg. Ex3) In nature, strontium has four stable isotopes. The 4 isotopes and their relative abundance are as follows: Sr-84 0.5% Sr-86 9.9% Sr- 87 7.0% Sr-88 82.6% Calculate the average atomic mass of Sr. Ch4 HW#4 10-15 Ch4 HW#4 10-15 10) How are isotopes of the same element alike? How are they different? 11) Three isotopes of oxygen are Oxygen – 16, Oxygen – 17, and Oxygen – 18, write the chemical symbol. 12) Determine # of prots, elects, Neuts for the 5 isotopes of zinc p+ Zn-64 Zn-66 Zn-67 Zn-68 Zn-70 e– no 13) There are 3 isotopes of silicon with mass #’s 28, 29, 30. The atomic mass of silicon is 28.086 amu. Which is most abundant? 14) The element copper has 2 naturally occurring isotopes: 63 29 Cu, 6529 Cu. The relative abundances are: Cu–63: 69.2% and Cu–65: 30.8% Calculate the average atomic mass. 13) There are 3 isotopes of silicon with mass #’s 28, 29, 30. The atomic mass of silicon is 28.086 amu. Which is most abundant? 14) The element copper has 2 naturally occurring isotopes: 63 29 Cu, 6529 Cu. The relative abundances are: Cu–63: 69.2% and Cu–65: 30.8% Calculate the average atomic mass. Cu – 63: 0.692 x 63 = Cu – 65: 0.308 x 65 = 15) The element mercury has 6 naturally occurring isotopes. The relative abundances are: Hg–198: 10%, Hg–199: 17%, Hg–200: 23%, Hg–201: 13%, Hg–202: 30%, Hg–204: 7%, Calculate the average atomic mass. Chapter 25.1 Nuclear Chemistry Ex: Carbon – 14 6P 8N What does the nucleus look like? Ex: Carbon – 14 What does the nucleus look like? It is more realistic to picture a nucleus as a swarm of bees, rather than a bunch of grapes. Ex: Carbon – 14 What does the nucleus look like? It is more realistic to picture a nucleus as a swarm of bees, rather than a bunch of grapes. Some isotopes of some elements contain and unstable ratio of protons to neutrons. These Radioisotopes are radioactive because they have unstable nuclei. They undergo radioactive decay The decay may be just a release of energy or it may be a complete break apart. Types of Radiation 1. Alpha radiation – a helium nucleus is emitted from a radioactive source Ex) 23892U → 22490Th Uranium – 238 Thorium – 234 + 4 2 He Alpha particle 4 He 2 238 U 92 Alpha radiation, aka: α emission, is: Low Energy Low Penetrating Power 224 Th 90 2. Beta radiation – an unstable nucleus decays, releases a beta particle - a neutron decomposes into a proton and an electron Ex1) 1 n 0 → Neutron Ex2) 14 C 6 1 H 1 + Proton → Radioactive Carbon – 14 ↑ p=6 n=8 14 N 7 Electron (beta particle) + Stable Nitrogen – 14 ↑ p=7 n=7 Beta radiation, aka: β emission, is: Mid Energy Mid Penetrating Power 0 e -1 0 e -1 Beta Particle 3. Gamma radiation – an unstable nucleus decays, releasing high energy electromagnetic radiation. Ex3) 23090Th Thorium – 230 → 226 Ra 88 Radon – 226 + 4 He 2 Alpha Particle Gamma radiation, aka: γ emission, is: High Energy High Penetrating Power + γ Gamma Radiation Ex4) Name the emitted particle and find the new nuclei created: a. 218 Fr→ 87 214 At 85 b. 241 Am 95 → c. 23592U → 90 Sr 38 4 He 2 + ____ + ____ + _____ + d. ____ + 23994Pu → 14458Ce + 9038Sr What happened to this poor plutonium? Ch25 HW#1 1 N 0 + 4 0-1e + 6 10n + 2 0-1e Ch25 HW#1 1) What part of the atom changes during radioactive decay? 2) Tell how alpha, beta, and gamma radiation are distinguished based on: a) atomic mass b) charge c) penetrating power α: β: γ: 3) The disintegration of the radioisotope radium-226 produces an isotope of the element radon and alpha radiation write eqn: 1) What part of the atom changes during radioactive decay? 2) Tell how alpha, beta, and gamma radiation are distinguished based on: a) atomic mass b) charge c) penetrating power α: β: γ: 4 2He 0 e -1 no mass, all energy +2 –1 no charge, all energy low mid high 3) The disintegration of the radioisotope radium-226 produces an isotope of the element radon and alpha radiation write eqn: 4) Write nuclear eqns: a) 30 15 P to 30 14 Si b) 13 6 12 C to 6 C 5) Complete: a) 3015P → 3016S + 0-1e b) 148O →147N + 0-1e c) 23892U → 23490Th + ___ d) 14156Ba → ___ + 0-1e 6) Beta decay the following: a) 9038Sr → b) 146C → c) 13755Cs → d) 23993Np → Ch25.2 Half Life aka: (t ½) - The time required for ½ the atoms of a radioisotope to decay. Ex 1) Nitrogen – 13 emits beta radiation (in the form of a positron) and decays to Carbon – 13 with a half life of 10 min. With a starting mass of 2.00g of N – 13, a) how long is 4 half lives? b) how many grams of N – 13 still exist after 3 half lives? Carbon Dating - developed in 1940’s - 146C → 147N + 0-1e - t1/2 = 5730 years - fairly accurately dates non-living things 200-50,000 yrs How do we date the dinos? Use a radioisotope with a longer ½ life - uranium – 238 → t1/2 = 4.5 x109 yrs (4.5 billion yrs!) - use this to age certain rocks, all the back to beginning of our solar system 4.6 billion years. Ex 2) What is the ½ life of this radioisotope ? If you had 20.0 g of it, how much remains after 10 years? 10075amt % 5025- 5 10 15 t (years) 20 25 Ex 2) What is the ½ life of this radioisotope ? 5 yrs If you had 20.0 g of it, how much remains after 10 years? 100(2 half-lives) 5g 75amt % 5025- 5 10 15 t (years) 20 25 Nuclear Fission and Fusion Fission-the splitting of a nucleus into smaller fragments caused by bombarding it with neutrons -releases enormous amounts of energy ( 1 kg of U-235 = 20,000 tons of TNT) → 235 U 92 236 U 92 91 Kr 36 Step 1: 10n + 23592U → 236 U 92 Step 2 23692U → 9136Kr + ___ + 3 10n Fusion – 2 nuclei combine to produce a nucleus of heavier mass In the sun: 4 1 H 1 + 2 0 e -1 → 4 He 2 + energy Fusion releases more energy than fission but requires high temps → 40,000,000 0C Cold fusion occurs at easily achievable temps: 2 H 1 Ch25 HW#2 + ___ → 4 He 2 + 1 n 0 + energy Ch25 HW#2 7 – 14 7) A sample of thorium – 234 has a half-life of 25 days. Will all the thorium undergo radioactive decay in 50 days? 8. Manganese-56 is a beta emitter with a half-life of 2.6h. What is the mass of manganese-56 in a 1-mg sample of the isotope after 10.4 h? 10.4 ÷ 2.6 = 4 half lives 9) Explain nuclear chain reaction. 10) How is the chain reaction controlled in a reactor? 11) Name a natural nuclear fusion reactor 12) What are advantages of producing electricity in a fusion reactor? 13) Write: a) a radon emits an alpha particle to form polonium – 218 b) Radium – 230 is produced when thorium 234 emits alpha c) When polonium – 210 emits alpha particle, product is Pb – 206 14. Graph the decay of Thorium 234 100 80 % 60 Remaining 40 20 20 40 60 80 100 days a) What percent after 60 days? b) How many grams of a 250g sample remain after 40 days? c) How many days would pass while 44g decayed to 11g? d) What is half-life? Ch4,25 Review 1. List the # of protons, neutrons, electrons for each atom: a. 2713 Al b. 4420 Ca c. 31H p: n: e: 2. What is the average mass of Lead? 204 Pb @ 1.37% 82 206 Pb @ 26.26% 82 207 Pb @ 20.82 % 82 208 Pb @ 51.55% 82 Element # of Protons Mass Number # of Atomic # Electrons Si Number Neutrons 15 1 2 50 88 24 38 Symbol 4. Charge Mass Penetrating Power alpha particle beta particle gamma ray 5. Complete the following nuclear equations: a. 2713 Al + 42 He 3014 Si b. 21483 Bi c. 2714 + ______ 42 He + ______ Si 0-1 e + ______ 6. A patient is administered 20 milligrams of iodime-131, how much of the isotope will remain in the body after 40 days if the half-life of I-131 is 8 days? 1 2 3 4 5 7. Know the science guys, Dalton’s atomic theory, and read your notes. Element Symbol Mass Atomic Protons Neutrons # # Krypton Lead 47 208 Mercury 125 121 Nitrogen 14 7 Potassium 39 20 Silver 61 Sodium 12 Sulfur 32 16 Uranium 146 Zinc 35 Period Group (Row) (Column) Electron Shells Worksheet 1. 1 1 Electron 1 H 1p 0n Hydrogen 1.0074 2. 2 1 3 Li Lithium 6.941 3p 4n 3. 2 3 _ __ _p _n Boron ______ 4. _ _ _ __ Nitrogen ______ _p _n 2 8 8 1 9. _ K _p _n Potassium ______ 10. 30 Zn Zinc 65 30p 35n 15) List the # of protons, neutrons, electrons a) 2713Al p+ no e- b) 4420Ca c) 31H d) 188O e) 7834Se