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PSC 1515
Energy in the Natural
Environment
Dr. Arturo Rodriguez
Miami Dade College
North Campus
Chapter 4
THE ATOM
This lecture will help you
understand:
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

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The Elements
The Periodic Table
Atoms Are Ancient, Tiny, and Empty
Protons and Neutrons
Isotopes and Atomic Mass
Probability Clouds and Atomic Orbitals
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The Elements
Atoms:
• make up all matter around us
• to date, 115 distinct kinds of atoms—
90 found in nature, remainder synthesized
Element
any material consisting of only one type of atom
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The Periodic Table
Periodic table:
• list of chemical elements
• designates each element by its atomic
symbol—first letter is capitalized
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Atoms Are Ancient, Tiny, and Empty
Atoms are
• ancient
—origin of most atoms goes back to birth of universe
• tiny
—first and lightest atom making up 90% of the
universe is hydrogen, H, followed by He
—in perpetual motion
—so small that when you inhale, you breathe atoms
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that
were once part of every person who ever lived
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Atoms Are Ancient, Tiny, and Empty
Atoms are
• tiny
—can’t be seen with visible light—smaller than the wavelength of
visible light
—made up of subatomic particles, protons and neutrons, in a
central nucleus surrounded by electrons
• mostly empty space
Elements heavier than hydrogen and much of the helium were produced
in the interiors of stars.
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Atoms Are Ancient, Tiny, and Empty
CHECK YOUR NEIGHBOR
Which of the following are incorrect statements about the
atom?
A.
B.
C.
D.
Atoms are smaller than the wavelength of visible light.
Atoms are mostly empty space, just as the solar system is mostly
empty space.
Atoms are perpetually moving.
Atoms are manufactured in plants, and in humans during
pregnancy.
Copyright © 2007 Pearson
Education, Inc., publishing
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Atoms Are Ancient, Tiny, and Empty
CHECK YOUR ANSWER
Which of the following are incorrect statements about the
atom?
A.
B.
C.
D.
Atoms are smaller than the wavelength of visible light.
Atoms are mostly empty space, just as the solar system is mostly
empty space.
Atoms are perpetually moving.
Atoms are manufactured in plants, and in humans during
pregnancy.
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as Pearson Addison
Wesley
Protons and Neutrons
Protons:
• carry a positive charge—same quantity of
charge as electrons
• are about 1800 times as massive as an electron
• have the same number of protons in the
nucleus as electrons surrounding the nucleus of
an electrically neutral atom
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Protons and Neutrons
Electrons:
• are identical
• repel electrons of neighboring atoms
• have electrical repulsion that prevents atomic
closeness
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Protons and Neutrons
Atomic number
is the number of protons in each element listed in
the periodic table.
Neutrons:
• accompany protons in the nucleus
• have about the same mass as protons but no
charge, so are electrically neutral
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Both protons and neutrons are nucleons.
Isotopes and Atomic Mass
Isotopes:
• refers to atoms of the same element that contain the
same number of protons but different numbers of
neutrons in the nucleus
• identified by mass number, which is the total number of
protons and neutrons in the nucleus
• differ only in mass and not by electric charge; therefore,
isotopes share many characteristics
Total number of neutrons
isotope
= mass number – atomic number
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Isotopes and Atomic Mass
Atomic mass:
• total mass of the atom(s) [protons, neutrons,
and electrons]
• listed in periodic table as atomic mass unit
One atomic mass unit is equal to
1.661 10–24 gram or 1.661 10–27 kg
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Isotopes and Atomic Mass
CHECK YOUR NEIGHBOR
The atomic number of an element matches the number of
A.
B.
C.
D.
protons in the nucleus of an atom.
electrons in a neutral atom.
both of the above.
none of the above.
Copyright © 2007 Pearson
Education, Inc., publishing
as Pearson Addison
Wesley
Isotopes and Atomic Mass
CHECK YOUR ANSWER
The atomic number of an element matches the number of
A.
B.
C.
D.
protons in the nucleus of an atom.
electrons in a neutral atom.
both of the above.
none of the above.
Comment:
When the atomic number doesn’t match the number of electrons,
the atom is an ion.
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Isotopes and Atomic Mass
CHECK YOUR NEIGHBOR
A nucleus with an atomic number of 44 and a mass number
of 100 must have
A.
B.
C.
D.
44 neutrons.
56 neutrons.
100 neutrons.
none of the above.
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Probability Clouds and Atomic Orbitals
Cutaway view of shells in the shell model of the
atom
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Probability Clouds and Atomic Orbitals
Shell model showing the first three periods of the
periodic table
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