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The Structure of Atoms

The Structure of Atoms

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The Structure of Atoms

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  1. 4 The Structure of Atoms

  2. Chapter Outline Subatomic Particles 次原子粒子 • Fundamental Particles基本粒子 • The Discovery of Electrons 電子的發現 • Canal Rays and Protons 陽極射線與質子 • Rutherford and the Nuclear Atom 拉塞福與核型原子 • Atomic Number原子序 • Neutrons 中子 • Mass Number and Isotopes 質量數和同位素 • Mass spectrometry and Isotopic Abundance 質譜儀和同位素豐量 • The Atomic Weight Scale and Atomic Weights化學原子量單位和原子量 • The Periodic Table: Metals, Nonmetals, and Metalloids 周期表: 金屬,非金屬和類金屬

  3. Chapter Outline The Electronic Structures of Atoms 原子的電子構造 11. Electromagnetic radiation電磁輻射 12. The Photoelectric Effect 光電效應 13. Atomic Spectra and the Bohr Atom 原子光譜和波耳原子模型 14. The Wave Nature of the Electron 電子具波的性質 15. The Quantum Mechanical Picture of the Atom 原子的量子力學架構 16. Quantum Numbers 量子數 17. Atomic Orbitals 原子軌道 18. Electron Configurations 電子組態 19. The Periodic Table and ElectronConfigurations 週期表與電子組態 20. Paramagnetism and Diamagnetism 順磁性及逆磁性

  4. Fundamental Particles基本粒子 • Three fundamental particles make up atoms. The following table lists these particles together with their masses and their charges. Table 4-1 Fundamental Particles of Matter Mass (amu) Particles Charge Electron 電子(e-) 0.00054858 -1 Proton 質子 (p, p+) 1.0073 +1 Neutron 中子 (n,n0) 1.0087 0

  5. The Discovery of Electrons • Humphrey Davy in the early 1800’s passed electricity through compounds and noted: • that the compounds decomposed into elements. • concluded that compounds are held together by electrical forces電力. • Michael Faraday in 1832-1833 realized that the amount of reaction that occurs during electrolysis電解is proportional to the electrical current passed through the compounds. 戴維 無機化學之父 法拉第 電學之父 第一、作個人的筆記 第二、持續的上課 第三、有讀書的同伴 第四、成立讀書會 第五、學習仔細觀察和精確的用字

  6. The Discovery of Electrons • Cathode Ray Tubes 陰極射線管experiments performed in the late 1800’s & early 1900’s. • Consist of two electrodes電極 sealed in a glass tube containing a gas at very low pressure. • When a voltage is applied to the cathodes a glow discharge is emitted. Collimator準直儀 把點光源發出的發散光或 其他輻射變成平行光束的器件 燈絲加熱陰極發射電子,加速和聚焦後形成電子束,陰性電子束會受到螢光屏的陽極吸引而正確投射

  7. The Discovery of Electrons • These “rays” are emitted from cathode (- end) and travel to anode (+ end). • Cathode Rays must be negatively charged! • J.J. Thomson modified the cathode ray tube experiments in 1897 by adding two adjustable voltage electrodes. • Studied the amount that the cathode ray beam was deflected by additional electric field.

  8. The Discovery of Electrons 陰極射線以直線行進 陰極射線具質量

  9. The Discovery of Electrons • Thomson used his modification to measure the charge to mass ratio of electrons. Charge to mass ratio 基本粒子的荷質比 e/m = -1.75881 x 108 coulomb/g of e- • Thomson named the cathode rays electrons. • Thomson is considered to be the “discoverer of electrons”. • TV sets and computer screens are cathode ray tubes. The coulomb (C)庫侖is the standard unit of quantity of electric charge.It is defined as the quantity of electricity transported in one second by a current of one ampere.

  10. The Discovery of Electrons • Robert A. Millikan won the 1st American Nobel Prize in 1923 for his famous oil-drop experiment 油滴實驗 • In 1909 Millikan determined the charge and mass of the electron

  11. The Discovery of Electrons • Millikan determined that the charge on a single electron = -1.60218 x 10-19 coulomb. • Using Thomson’s charge to mass ratio we get that the mass of one electron is 9.11 x 10-28 g. • e/m = -1.75881 x 108 coulomb • e = -1.60218 x 10-19 coulomb • Thus m = 9.10940 x 10-28 g

  12. Canal Rays陽極射線and Protons質子 • Eugene Goldstein noted streams of positively charged particles in cathode rays in 1886. • Particles move in opposite direction of cathode rays. • Called “Canal Rays” because they passed through holes (channels or canals) drilled through the negative electrode. • Canal rays must be positive. • Goldstein postulated the existence of a positive fundamental particle called the “proton”. Atom  cation++ e- 陰極 陽極 Canal rays particles have e/m ratios many smaller than those of electrons because of their much greater masses

  13. Rutherford拉塞福and the Nuclear Atom 核型原子 How are these charge distributed? • Ernest Rutherford directed Hans Geiger蓋革and Ernst Marsden’s馬斯頓experiment in 1910. • - particle scattering from thin Au foils • Gave us the basic picture of the atom’s structure. • 散射a粒子到金箔並且觀察到大角度的散射,提出了原子有很小、密度大且帶正電的核 Undeflected α particles Source of narrow beam of fast-moving a particle (positive charge) Deflected particles ZnS fluorescent screen

  14. Rutherford and the Nuclear Atom In 1912 Rutherford decoded the -particle scattering information • Explanation involved a nuclear atom with electrons surrounding the nucleus

  15. Rutherford and the Nuclear Atom Rutherford’s major conclusions from the -particle scattering experiment • The atom is mostly empty space. • It contains a very small, dense center called the nucleus. • Nearly all of the atom’s mass is in the nucleus. • The nuclear diameter is 1/10,000 to 1/100,000 times less than atom’s radius.

  16. Rutherford and the Nuclear Atom • Because the atom’s mass is contained in such a small volume: • The nuclear density is 1015g/mL. • This is equivalent to 3.72 x 109 tons/in3. • Density inside the nucleus is almost the same as a neutron star’s density. Rutherford Model of the atom: Atoms consist of very small, very dense positively charged nuclei surrounded by clouds of electrons at relatively large distances from the nuclei

  17. Atomic Number原子序 • The atomic number is equal to the number of protons in the nucleus • Sometimes given the symbol Z • On the periodic chart Z is the uppermost number in each element’s box • In 1913 H.G.J. Moseley realized that the atomic number determines the element • The elements differ from each other by the number of protons in the nucleus. • The number of electrons in a neutral atom is also equal to the atomic number.

  18. Neutrons 中子 • James Chadwick 查兌克 in 1932 analyzed the results of -particle scattering on thin be films. • Chadwick recognized existence of massive neutral particles which he called neutrons. • Chadwick discovered the neutron. Atoms consist of very small, very dense positively charged nuclei surrounded by clouds of electrons at relatively large distances from the nuclei. All nuclei contain protons; nuclei of all atoms except the common form of hydrogen also contain neutrons

  19. Mass Number質量數 and Isotopes同位數 • Mass number is given the symbol A. • A is the sum of the number of protons and neutrons. • Atomic number Z = proton number N = neutron number • Mass number A = Z + N • A common symbolism used to show mass and proton numbers is • Can be shortened to this symbolism. A 107 63 197 14 12 40 Efor example Cu N Ag Au Ca C Z 79 20 6

  20. Mass Number and Isotopes • Isotopes are atoms of the same element but with different neutron numbers • Isotopes have different masses and A values but are the same element • Display very similar chemical properties • One example of an isotopic series is the hydrogen isotopes the most common hydrogen . a radioactive hydrogen isotope

  21. Mass Number and Isotopes • The stable oxygen isotopes provide another example. • 16O is the most abundant stable O isotope. • How many protons and neutrons are in 16O? 8 protons and8 neutrons • 17O is the least abundant stable O isotope. • How many protons and neutrons are in 17O? 8 protons and 9 neutrons • 18O is the second most abundant stable O isotope. • How many protons and neutrons in 18O? 8 protons and 10 neutrons

  22. Example 4-1 Determination of Atomic Makeup Determine the number of protons, neutrons, and electrons in each of the following species. Are the members within each pair isotopes? (a) (b) (a)Atomic number=17, 17protons/nucleus mass number =35 18 neutrons Because no charge is indicated: 17 electrons These are isotopes of the same element (b) These are isotopes of the same element 63 37 35 65 63 37 65 35 Cl and Cu and Cu Cl Cl Cl 17 protons, 20 neutrons, and 17 electrons Cu 29 protons, 34 neutrons, and 29 electrons Cu 29 protons, 36 neutrons, and 29 electrons 17 29 17 17 29 29 17 29 Exercise 18, 20

  23. Mass Spectrometry質譜儀andIsotopic Abundances • Francis Aston devised the first mass spectrometer. 英國物理學家,因研製質譜儀並用以準確測量原子及分子質量以及發現大量核素,獲1922年諾貝爾化學獎 • 質譜儀(mass spectrometry, MS)是以熱電子撞擊氣體分子,使產生碎片及離子,再經磁場分離,依據質荷比之測量,來決定分子質量的技術。 • There are four factors which determine a particle’s path in the mass spectrometer. 1. accelerating voltage –電場強度 2. magnetic field strength– 磁場強度 3. masses of particles–物質質量 4. charge on particles –物質電荷

  24. Mass Spectrometry質譜儀andIsotopic Abundances 基本原理 (1).將不同型態的樣品〈氣、液、固相〉導入質譜儀。 (2).樣品分子在離子源內游離(ionization)成氣相之離子形式。 (3).依質荷比(m/z : mass to charge ratio)不同分離各個樣品離子。 (4).各樣品離子到達偵測器被偵測出來。 (5).在資料處理系統中,離子偵測訊號被轉換成可讀或圖譜方式呈現。

  25. Mass Spectrometry andIsotopic Abundances • Mass spectrum of Ne+ ions shown below. • How scientists determine the masses and abundances of the isotopes of an element. 組成比例 Isotope abundances: the relative amounts of the isotopes 同位素豐量 (isotopic abundance):為某種同位素在此元素之各種同位素中所占的原子百分比。

  26. Amodern mass spectrum

  27. The Atomic Weight Scale原子量單位and Atomic Weights原子量 • If we define the mass of 12C as exactly 12 atomic mass units (amu)原子質量單位, then it is possible to establish a relative weight scale for atoms. • 1 amu = (1/12) mass of 12C by definition • What is the mass of an amu in grams?

  28. The Atomic Weight Scale and Atomic Weights • The atomic number Z =proton number in the nucleus = electrons (in a neutral atom) • The Mass Number A = proton number +neutron number • The atomic weight of an element is the weighted average of the masses of its stable isotopes • Atomic number Z = proton number • N = neutron number • Mass number A = Z + N A E Z

  29. The Atomic Weight Scale and Atomic Weights • Example 4-2: Naturally occurring Cu consists of 2 isotopes. It is 69.1% 63Cu with a mass of 62.9 amu, and 30.9% 65Cu, which has a mass of 64.9 amu. Calculate the atomic weight of Cu to one decimal place. 63Cu isotope 65Cu isotope Atomic weight= (0.691)x(62.9 amu)+(0.309)x(64.9amu) =63.5 amu for copper

  30. The Atomic Weight Scale and Atomic Weights • Example 4-3: Naturally occurring chromium consists of four isotopes. It is 4.31% 2450Cr, mass = 49.946 amu, 83.76% 2452Cr, mass = 51.941 amu, 9.55% 2453Cr, mass = 52.941 amu, and 2.38% 2454Cr, mass = 53.939 amu. Calculate the atomic weight of chromium. Atomic weight= (0.6431x49.946 amu)+(0.8376x51.941 amu) +(0.0955x52.941 amu)+(0.0238x53.939 amu) =51.998 amu for chromium

  31. The Atomic Weight Scale and Atomic Weights • Example 4-4: The atomic weight of boron is 10.811 amu. The masses of the two naturally occurring isotopes 510B and 511B, are 10.013 and 11.009 amu, respectively. Calculate the fraction and percentage of each isotope. Let the 10B fraction is x 11.811amu = (x x 10.013 amu)+((1-x) x 11.009amu) =(10.013x+11.009-11.009x)amu (11.811-11.009) amu=(10.013-11.009)xamu x=0.199 5 % abundance of 10B is 19.1% 5 % abundance of 11B = 100%-19.1% = 80.9% 5 Textbook example 4-2 and 4-3 p132-133

  32. The Atomic Weight Scale and Atomic Weights Example 4-2 Calculation of Atomic Weight Three isotopes of magnesium occur in nature. Their abundances an masses, determined by mass spectrometry, are listed in the following table. Use this information to calculate the atomic weight of magnesium. Isotope %Abundance Mass (amu) 24Mg 78.99 23.98504 25Mg 10.00 24.98584 26Mg 11.01 25.98259 Atomic weight = 0.7899 x (23.98504amu) + 0.1000 x (24.98584 amu) + 0.1101 x (25.98259 amu) =18.946amu+2.4986amu+2.8607amu = 24.30 amu Exercise 28, 30

  33. The Atomic Weight Scale and Atomic Weights Example 4-3 Calculation of Iostope Abundance The atomic weight of gallium is 69.72 amu. The masses of the naturally occurring isotopes are 69.9257 amu for 69Ga and 70.9249 amu for 71Ga. Calculate the percent abundance of each isotope. Let x =fraction of 69Ga Then (1-x)= fraction of 71Ga x x (69.9257amu) + (1-x) x (70.9249amu) = 69.72amu 68.9257x + 70.9249-70.9249 x =69.72 -1.992x = -1.20 x = 0.6 x = fraction of 69Ga 60.00% 69Ga (1-x )= 0.4=fraction of 71Ga  40.00% 71Ga Exercise 32

  34. The Periodic Table: Metals, Nonmetals, and Metalloids • 1869 - Mendeleev & Meyer • Discovered the periodic law • The properties of the elements are periodic functions of their atomic numbers.

  35. The Periodic Table: Metals, Nonmetals, and Metalloids周期表: 金屬、非金屬、類金屬 • Groups or families(族) • Vertical group of elements on periodic table • Similar chemical and physical properties 鉻 鎢 鉬

  36. Group (族) 鈹 鋰 鎂 鈉 鈣 鉀 鍶 銣 鋇 銫 鐳 鍅

  37. The Periodic Table: Metals, Nonmetals, and Metalloids • Period(週期) • Horizontal group of elements on periodic table • Transition from metals to nonmetals • Increasing atomic number原子序 鈹 硼 碳 鋰 氮 氟 氧 氖

  38. 金屬 鈍 氣 鹵 素 非金屬 類金屬 過渡元素 Most active nonmetal Most active Naturally occur * 鹼 金 屬 鹼 土 金 屬 鑭系元素 錒 系 元 素

  39. The Periodic Table: Metals, Nonmetals, and Metalloids • Table 4-6 Some physical properties of metals • High electrical conductivity that decreases with increasing temperature 導電性 ( 溫度升高導電性降低) • High Thermal conductivity導熱性 • Metallic gray or silver luster 具金屬光澤 • Almost all are solids • Malleable (can be hammered into sheets) 可塑性 • Ductile (can be drawn into wires)具展延性 • Table 4-6 Some physical properties of nonmetals • Poor electrical conductivity (except carbon) • Good heat insulators (except carbon) • No metallic luster • Solid, liquid or gases • Brittle in solid state • Nonductile

  40. The Periodic Table: Metals, Nonmetals, and Metalloids • Table 4-7 Some chemical properties of metals • Outer shells contain few electrons—three or fewer • Form cations by losing electrons(易失電子而帶正電) • Form ionic compounds with nonmetals • 與非金屬形成離子化合物 • Solid state characterized by metallic bonding 金屬鍵結 • Table 4-7 Some chemical properties of nonmetals • Outer shells contain four or more electrons • Form anion by gating electrons (易得電子而帶負電) • Form ionic compounds with metalsand molecular (covalent) other compounds with nonmetals • Covalently bonded molecules共價分子; noble gases are monatomic

  41. The Periodic Table: Metals, Nonmetals, and Metalloids Metallic character increases from top to bottom and decreases from left to right with respect to position in the periodic table Nonmetallic character decreases from top to bottom and increases from left to right with respect to position in the periodic table

  42. The Periodic Table: Metals, Nonmetals, and Metalloids Metalloid 類金屬 • Some properties that are characteristic of both metals and nonmetals • Some act as semiconductors半導體: such as silicon矽, germanium鍺, antimony銻 • insulators at lower temperature • Become conductors at higher temperature • Aluminum is the least metallic of the metals and is sometimes classified as a metalloid • It is metallic in appearance and an excellent conductor of electricity

  43. The Periodic Table: Metals, Nonmetals, and Metalloids • Group IA metals (Alkali metals鹼金屬) • Li, Na, K, Rb, Cs, Fr • One example of a periodic trend • The reactions with water of Li, Na, & K

  44. The Periodic Table: Metals, Nonmetals, and Metalloids • Group IIA metals • alkaline earth metals鹼土金屬 • Be, Mg, Ca, Sr, Ba, Ra

  45. The Periodic Table: Metals, Nonmetals, and Metalloids • Group VIIA nonmetals • Halogens鹵素 • F, Cl, Br, I, At

  46. The Periodic Table: Metals, Nonmetals, and Metalloids • Group VIA nonmetals • O, S, Se, Te

  47. The Periodic Table: Metals, Nonmetals, and Metalloids • Group 8A nonmetals • noble, inert or rare gases • He, Ne, Ar, Kr, Xe, Rn

  48. Electromagnetic Radiation電磁輻射 • 以電磁波方式在自由空間或實物媒質中傳播的能量,例如無線電波、可見光和γ射線。 • The wavelength波長of electromagnetic radiation has the symbol . • Wavelength is the distance from the top (crest) of one wave to the top of the next wave. • Measured in units of distance such as m,cm, Å. • 1 Å = 1 x 10-10 m = 1 x 10-8 cm • The frequency頻率of electromagnetic radiation has the symbol . • Frequency is the number of crests or troughs that pass a given point per second. • Measured in units of 1/time - s-1

  49. 電磁輻射 • 以具能量之光子形式,以光速 (3 x 1010 cm/sec)於空間中移動 • 能量(電子伏特,eV表之)與頻率成正比,與波長呈反比 • 高能量光子具長射程、強穿透力 (遠離發射源仍具影響力) • 依能量強弱分為游離輻射與非游離輻射