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Slide 1 of 25 Chemistry 4.2. © Copyright Pearson Prentice Hall Slide 2 of 25 Structure of the Nuclear Atom Cathode-ray tubes are found in TVs, computer.

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Presentation on theme: "Slide 1 of 25 Chemistry 4.2. © Copyright Pearson Prentice Hall Slide 2 of 25 Structure of the Nuclear Atom Cathode-ray tubes are found in TVs, computer."— Presentation transcript:

1 Slide 1 of 25 Chemistry 4.2

2 © Copyright Pearson Prentice Hall Slide 2 of 25 Structure of the Nuclear Atom Cathode-ray tubes are found in TVs, computer monitors, and many other devices with electronic displays. 4.2

3 © Copyright Pearson Prentice Hall Structure of the Nuclear Atom > Slide 3 of 25 Subatomic Particles What are three kinds of subatomic particles? 4.2

4 © Copyright Pearson Prentice Hall Structure of the Nuclear Atom > Slide 4 of 25 4.2 Subatomic Particles Three kinds of subatomic particles are electrons, protons, and neutrons.

5 © Copyright Pearson Prentice Hall Structure of the Nuclear Atom > Slide 5 of 25 Cathode Ray Tube William Crookes used a glass tube that was used to study the relationship between mass and charge. Metal electrodes were placed in each end of the tube. The metal plate that was connected to the negative terminal of the battery was called the cathode. Electrode connected to the positive terminal was called the Anode.

6 © Copyright Pearson Prentice Hall Structure of the Nuclear Atom > Slide 6 of 25 Cathode Ray tube

7 © Copyright Pearson Prentice Hall Structure of the Nuclear Atom > Slide 7 of 25 The Real thing!

8 Slide 8 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Subatomic Particles Electrons In 1897, the English physicist J. J. Thomson (1856–1940) discovered the electron. Electrons are negatively charged subatomic particles. 4.2

9 Slide 9 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom In the mid-nineteenth century, Julius Plücker investigated the light emitted in discharge tubes (Crookes tubes) and the influence of magnetic fields on the glow.Julius Plücker discharge tubesCrookes tubes Later, in 1869, Johann Wilhelm Hittorf studied discharge tubes with energy rays extending from a negative electrode, the cathode.Johann Wilhelm Hittorfelectrode These rays produced a fluorescence when they hit a tube's glass walls, and when interrupted by a solid object they cast a shadow.fluorescence

10 Slide 10 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Subatomic Particles Thomson performed experiments that involved passing electric current through gases at low pressure. The result was a glowing beam, or cathode ray, that traveled from the cathode to the anode. 4.2

11 Slide 11 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Subatomic Particles Cathode Ray Tube 4.2

12 Slide 12 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom In a cathode-ray tube, electrons travel as a ray from the cathode (-) to the anode (+). A television tube is a specialized type of cathode-ray tube.

13 Slide 13 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Thomson examined two ways that a cathode ray can be deflected: a) by using a magnet, and b) by using electrically charged plates. Inferring If a cathode ray is attracted to a positively charged plate, what can you infer about the charge of the particles that make up the cathode ray?

14 Slide 14 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Subatomic Particles A cathode ray is deflected by a magnet. 4.2

15 Slide 15 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Subatomic Particles A cathode ray is deflected by electrically charged plates. 4.2

16 Slide 16 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Subatomic Particles Thomson concluded that a cathode ray is a stream of electrons. Electrons are parts of the atoms of all elements. 4.2

17 Slide 17 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Subatomic Particles Protons and Neutrons In 1886, Eugen Goldstein (1850–1930) observed a cathode-ray tube and found rays traveling in the direction opposite to that of the cathode rays. He concluded that they were composed of positive particles. Such positively charged subatomic particles are called protons. 4.2

18 Slide 18 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Goldstien canal tube PerforatedCathode

19 Slide 19 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Electron in bottom Protons are red (Green)

20 Slide 20 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Subatomic Particles In 1932, the English physicist James Chadwick (1891–1974) confirmed the existence of yet another subatomic particle: the neutron. He work under Rutherford research. Neutrons are subatomic particles with no charge but with a mass nearly equal to that of a proton. 4.2

21 Slide 21 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom He devised a simple apparatus that consisted of a cylinder containing a polonium source and beryllium target. The resulting radiation could then be directed a material such as paraffin wax and the particles displaced, which were protons, would go into a small ionisation chamber where they could be detected with an oscilloscope.

22 Slide 22 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom

23 Slide 23 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Oscilloscope

24 Slide 24 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Subatomic Particles Table 4.1 summarizes the properties of electrons, protons, and neutrons. 4.2

25 © Copyright Pearson Prentice Hall Structure of the Nuclear Atom > Slide 25 of 25 The Atomic Nucleus How can you describe the structure of the nuclear atom? 4.2

26 Slide 26 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom The Atomic Nucleus J.J. Thompson and others supposed the atom was filled with positively charged material and the electrons were evenly distributed throughout. This model of the atom turned out to be short- lived, however, due to the work of Ernest Rutherford (1871–1937). 4.2

27 Slide 27 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom The Atomic Nucleus Ernest Rutherford’s Portrait Born in New Zealand, Nobel Prize 1908 4.2

28 Slide 28 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom The Atomic Nucleus Rutherford’s Gold-Foil Experiment In 1911, Rutherford and his coworkers at the University of Manchester, England, directed a narrow beam of alpha particles at a very thin sheet of gold foil. 4.2

29 Slide 29 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom The Atomic Nucleus Rutherford’s Gold-Foil Experiment 4.2

30 Slide 30 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom Gold Foil Experiment yield that an atomic nucleus is present. Most of the particles passed through but some were deflect. He measured the angle of deflection. The experiment indicated the atom was made mostly of space. The nucleus is were the mass and positive charge is concentrated. Nucleus deflected the particles.

31 Slide 31 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom The Atomic Nucleus Alpha particles scatter from the gold foil. 4.2

32 Slide 32 of 25 © Copyright Pearson Prentice Hall > Structure of the Nuclear Atom The Atomic Nucleus The Rutherford Atomic Model Rutherford concluded that the atom is mostly empty space. All the positive charge and almost all of the mass are concentrated in a small region called the nucleus. The nucleus is the tiny central core of an atom and is composed of protons and neutrons. 4.2

33 © Copyright Pearson Prentice Hall Structure of the Nuclear Atom > Slide 33 of 25 The Atomic Nucleus In the nuclear atom, the protons and neutrons are located in the nucleus. The electrons are distributed around the nucleus and occupy almost all the volume of the atom. Proton and neutrons 99% of mass Electron make up 99% of volume 4.2

34 © Copyright Pearson Prentice Hall Slide 34 of 25 Section Quiz -or- Continue to: Launch: Assess students’ understanding of the concepts in Section 4.2 Section Quiz 4.2.

35 © Copyright Pearson Prentice Hall Slide 35 of 25 4.2 Section Quiz 1. Which of the following is NOT an example of a subatomic particle? a.proton b.molecule c.electron d.neutron

36 © Copyright Pearson Prentice Hall Slide 36 of 25 4.2 Section Quiz 2. The nucleus of an atom consists of a.electrons only. b.protons only. c.protons and neutrons. d.electrons and neutrons.

37 © Copyright Pearson Prentice Hall Slide 37 of 25 4.2 Section Quiz 3. Most of the volume of the atom is occupied by the a.electrons. b.neutrons. c.protons and neutrons. d.protons.

38 END OF SHOW


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