chemistry 4.2
Post on 30-Dec-2015
37 Views
Preview:
DESCRIPTION
TRANSCRIPT
Slide 1 of 25
Chemistry 4.2
© Copyright Pearson Prentice Hall
Structure of the Nuclear Atom >
Slide 2 of 25
4.2 Subatomic Particles
Three kinds of subatomic particles are electrons, protons, and neutrons.
Slide 3 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
Slide 4 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
Slide 5 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom Subatomic Particles
Cathode Ray Tube
4.2
Slide 6 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom Subatomic Particles
A cathode ray is deflected by a magnet.
4.2
Slide 7 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom Subatomic Particles
A cathode ray is deflected by electrically charged plates.
4.2
Slide 8 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom
Let’s go to the videotape
Slide 9 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom Thomson’s Conclusions
Thomson found:
1.The charge to mass ratio of the particle
2.Various metals produced the exact same cathode ray (same charge to mass)
3.Various gases produced the exact same cathode ray (same charge to mass)
Slide 10 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom Subatomic Particles
Thomson concluded that a cathode ray is a fundamental particle contained in all matter.
It is made of a stream of electrons. Electrons are parts of the atoms of all elements.
4.2
Slide 11 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom Robert Millikan
Slide 12 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom
Let’s go to the videotape!!
Slide 13 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom Robert Millikan
Millikan determined:
1.The charge on an electron.
2.The fundamental charge of matter.
3.He calculated the mass of an electron from Thomson’s charge to mass ratio.
Slide 14 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom Conclusions
•Atom is divisible
•One of the basic subatomic particles is the negatively charged electron
•Atom is electrically neutral, so it must contain positive charges to balance out the electrons
•Electrons have an extremely small mass, therefore there must be other massive particles in the atom
Slide 15 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
Slide 16 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.
Neutrons are subatomic particles with no charge but with a mass nearly equal to that of a proton.
4.2
Slide 17 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
Slide 18 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 was called the “plum pudding model,” but you can think of it as the “chocolate chip cookie model.”
This model of the atom turned out to be short-lived, however, due to the work of Ernest Rutherford (1871–1937).
4.2
Slide 19 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
Slide 20 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom The Atomic Nucleus
Rutherford’s Gold-Foil Experiment
4.2
Slide 21 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom The Atomic Nucleus
Alpha particles scatter from the gold foil.
4.2
Slide 22 of 25
© Copyright Pearson Prentice Hall
>Structure of the Nuclear Atom
Video
Slide 23 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
© Copyright Pearson Prentice Hall
Structure of the Nuclear Atom >
Slide 24 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.
4.2
END OF SHOW
top related