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Ch 4 – Atomic Structure

Ch 4 – Atomic Structure. History: Democritus- (400 BC) What’s the smallest possible particle? Break a rock into pieces… eventually get to smallest possible pieces → call those “ atomis ” (invisible) 2. Aristotle- Everything is made of a substance called “ hyle .” Re-arrange hyle to make

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Ch 4 – Atomic Structure

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  1. Ch 4 – Atomic Structure • History: • Democritus- (400 BC) What’s the smallest possible particle? Break a rock into pieces… • eventually get to smallest possible pieces → call those “atomis” (invisible) • 2. 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. • Dalton- (1800’s) father of atomic theory • All elements composed of tiny, invisible particles →atoms • All atoms of same element are identical atoms of different elements are different • Atoms of diff. elements combine in whole # ratios. • Chem. occur when atoms separate from each other, join with others, but the atoms • themselves never change. • JJ Thompson (~1900) uses cathode ray tube & discovers the electron

  2. 5. Millikan (~1900) his oil drop experiment discovered mass/charge of electron 6. Rutherford- (1905)- Gold Foil Experiment – discovered the nucleus →(+) charged core of the atom 7. Neils Bohr- (~1910’s)- Planetary model of the atom 8. Chadwick- (1932)- discovered neutron

  3. 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

  4. Ch. 4 HW #1 1-5 • Explain how Democritus came up with his theory every made of atoms: • Which statement would Dalton Agree with: • Atoms are the smallest particles of matter. • Mass of an iron atom is different from mass of a copper atom. • Every atom of silver is Identical to every other atom of silver. • A compound is composed of atoms of two or more different elements.

  5. 3. Since all atoms have negatively charged electrons shouldn’t every sample of matter have a negative charge? Explain. 4. Now did the results of Rutherford's Gold Foil Experiment differ from his expectations? 5. What is the charge of every nucleus (+ or -)?

  6. Ch 4 HW #2 • 6. (in class) • 7. (in class) • 8. An atom is identified as platinum- 195. • What is the number 195 called? • What is the symbol with #’s?

  7. 9. Determine the number of neutrons: Carbon - 13 Nitrogen- 15 Radium - 226

  8. Ch 1 – XC Clock Suppose a metric clock used the following system: 1 day = 10 metric hours 1metric hour = 10 metric minutes 1 metric minute = 10 metric seconds 1 metric second = 10 metric mini-seconds If the metric clock reads 4hrs, 5min, 6 sec, 7 mini-sec, What time is it in the real world?

  9. Ch 4- The Periodic Table 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 neutron - do not count electrons → too small! • 2 • 4 • C • Carbon • 12.011

  10. HW # 6) (copy to separate paper!) HW # 7)

  11. Writing symbols: 16 ← mass # (prots & nuets) ex: 8 ← Atomic # (prots) Neutrons = mass- atomic = 16 – 8 = 8 Neutrons ex: 108 Ag Neutrons = 108 – 47 = 61 N 47 Sometimes written is this form : ex: Carbon – 12 Back to P.T. ↖ mass # Look at P.T. to find atomic # Neutrons = Mass – Atomic = 12 – 6 = 6 neutrons ex: Uranium – 238 Neutrons = 238 – 92 = 146 6 2 4 C Carbon 12.011

  12. Average Atomic Mass 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 14) Cu had 2 isotopes: Cu – 63 , Cu – 65. Given that the ave atomic mass is 63.546 amu, which isotope is more abundant? (finish for HW) Calculating Ex) Element x has 2 natural isotopes. One isotope with mass 10.012 amu has a relative abundance of 80.09%. Calculate the atomic mass and the name of the element. 10X: 10.012 amu x 0.1991 = “X: 11.009 amu x 0.8009 = Ch 4 HW # 4 10-15

  13. Isotopes Isotopes of the SAME ELEMENT obviously have the same # of protons, differ in # of Neutrons Ex. Write the chemical symbol and find # of Neutrons for: Carbon-12 and Carbon-13 126 C 136 C HW #12) Determine # of prots, elects, Neuts for the 5 isotopes of zinc p+ e- N Zn-64 30 30 34 Zn-66 30 30 36 Zn-67 30 30 37 Zn-68 30 30 38 Zn-70 30 30 40

  14. Atomic Mass ↓ .00000000000000000000003g 1 Flourine atom-3.155x10-23 g 1 arsenic atom-1.244x10-22 g Not practical! Decide to call the mass of 1 proton=1 atomic mass unit -since prots and Neuts are close, but slightly different, decide to take Carbon-12 (6 prots, 6 Neuts) ÷ by 12 = 1 amu

  15. Electron Shells Worksheet 1. 1 1 H Hydrogen 1.0074 1 Electron 1p 0n 2. 2 1 3 Li Lithium 6.941 2. 2 1 3 Li Lithium 6.941 3p 4n

  16. 3. 2 3 _ __ Boron ______ _p _n 4. _ _ _ __ Nitrogen ______ _p _n

  17. 5. 2 8 2 12 Mg Magnesium 24.3 12p 18n 6. _ _ _ __ Aluminum ______ _p _n

  18. 7. 2 8 7 _ __ Chlorine ______ _p _n 8. 2 8 8 _ __ Argon ______ _p _n

  19. 2 8 8 1 _ K Potassium ______ 9. _p _n 10. 30 Zn Zinc 65 30p 35n

  20. Ch 4 HW #3 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) ( in class ) 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 : 6329 Cu, 6529 Cu. The relative abundances and atomic masses are: Calculate the average atomic mass. Cu – 63 .692 x 63 = 43.47 Cu – 65 .308 x 65 = 20.02 63.49

  21. 15) List the # of protons, neutrons, electrons

  22. Chapter 25 Nuclear Chemistry Ex: Carbon – 14 Radioisotopes – isotopes that are radioactive because they have unstable nuclei. They undergo radioactive decay - give up energy from the nuclei ( some nuclei break apart. ) 68PN Types of Radiation Alpha radiation – a helium nucleus is emitted from a radioactive source Ex) 23892 U → 22490Th + 42 He Uranium – 238 Thorium – 234 Alpha particle (α emission) Low Energy Low Penetrating Power 42 He 238 92U 22490Th

  23. Beta radiation – an unstoppable nucleus decays, releases a beta particle - a neutron decomposes into a proton and an electron 10N → 11H + 0-1e Neutron Proton Electron (beta particle) Ex) 146C → 147N + 0-1e Radioactive Stable Beta Carbon – 14 Nitrogen – 14 Particle ↑ ↑ p=6 p=7 N=8 N=7 Gamma radiation – an unstable nucleus decays, releasing high energy electromagnetic radiation. Ex) 23090Th → 22688Ra + 42He + Y Thorium – 230 Radon – 226 Alpha Gamma Particle Ray

  24. Name the emitted particle and find the new nuclei created: Ex) 21887fr → 21485At + 42He 24195Am → 42He + 23793Np 23592U → 9038Sr + 14458Ce + 10N + 4 0-1e 10N + 23994Pu → 14458Ce + 9038Sr + 6 10N + 2 0-1e

  25. Ch 25 HW#1 What part of the atom changes during radioactive decay? Tell how alpha beta and gamma radiation are distinguished based on: a) mass b) charge c) penetrating power 4 2 0-1β 3) The disintegration of the radioisotope radium-226 produces an isotope of the element radon and alpha radiation write eqn: 22688 Ra → 222 88 Rn + 4 2

  26. 4) Write nuclear eqns: (positron) a) 3015 P to 3014 Si 30 15 P → 30 14 Si + 01β b) 136 C to 12 6 C 13 6 C → 12 6 C + 10 n 5) Complete: a) 3015P → ____ + 0-1e b) ___ →147N + 0-1e c) 23892U → 23490Th + ___ d) 14156BA → ___ + 0-1e 6) Beta decay the following: a) 9038Sr → b) 146C → c) 13755Cs → d) 23993Np →

  27. Half Life (t ½) • The time required for ½ the atoms of a radioisotope to decay. • Ex 1) Nitrogen – 13 emits beta radiation and decays to Carbon – 13 with a half life of 10 min. • with a starting mass of 2.00gof 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 ( 4,500,000,000,) ( 4.5 billion yrs ) • - use this to age certain rocks, all the back to beginning of • our solar system 4.6 billion years.

  28. 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? 2 half-lives 5g 100- 50- amt % 25- 5 10 15 20 25 t(yrs)

  29. 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 = 20000 tons of TNT) → ↗ ↘ 23592 U 23692 U 9136 Kr 10 N + 23592 U → 23692 U → 91 36 Kr + ___ + 3 10 N

  30. Fusion – 2 nuclei combine to produce a nucleus of heavier mass In the sun: 4 11H + 2 0-1e → 42He + energy - fusion releases more energy than fission but requires high temps → 40,000,000 0C Cold fusion 21H + 31H → 42He + 10N + energy

  31. Ch 25 HW #2 7) A sample of thorium – 234 has a half-life of 25 days. Will all the thorium undergo radioactive decay in 50 days? 10g → 5g → 2.5g 9) Explain nuclear chain reaction. 10) How is the chain reaction uncontrolled 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 Rn → He + Po b) Radium – 230 is produced when thorium 234 emits alpha c) When polonium – 210 emits alpha particle, product is Pb – 206 Po → Ne + Pb

  32. Graph the decay of Thorium 234 What percent after 60 days? 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? 100 80 60 Remaining % 40 20 20 40 60 80 100 Days

  33. Ch 3, 4, 25 Reviews • Ch 3 – how many seconds are in 3.7 days? • 3.7 days 24hrs 60 min 60sec • 1days 1hrs 1min = sec • What values does 5.0g of Al occupy ( density of Al is 2.80g/Dm3 ) • Ch 6 – 30)

  34. 32) List the # of Protons, Neutrons, Electrons for each 2713Al b) 4420Ca c) 31H 43) What is the average mass of lead? 20482Pb @ 1.37% 20682Pb @ 26.26% 20782Pb @ 20.82% 20882Pb @ 51.55% Ch 25 – 24 ) Write the symbol and state the charge for each: a) alpha particle b) beta particle c) gamma ray

  35. 34) A patient is administered 20mg of iodine – 131, How much of the isotope will remain In the body after 40 days id the half-life of I – 131 is 8 days? 1 2 3 4 5 20mg → 10mg → 5mg → 2.5mg → 1.25mg ↙ .625mg

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