2.1 Getting to Know the Atom
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Transcript of 2.1 Getting to Know the Atom
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A Look at NuclearScience and Technology
Larry Foulke
2.1 Atomic and Nuclear Physics The Einstein Connection
Getting to know the atom
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Image Source: See Note 1
The Einstein Connection
E=mc2
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The Atom
Image Source: See Note 2
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The Atom Electrons Negatively charged, light-weight particles that orbit the nucleus. Involved in forming chemical bonds with other atoms
Protons Positively charged, heavy particles in the atomic nucleus. Number of protons determines the element and all physical
properties of atom.
Neutrons Charge-less, heavy particles in atomic nucleus Neutrons stabilize the nucleus. To few or too many neutrons will
make a nucleus unstable.
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The Atom Atoms are identified byAtomic Number (Z): Number of protons in the
nucleus. Determines what element the atom is.
Atomic Mass (A): Total weight of the atom, equal tonumber of protons + number of neutrons. (A=Z+N)
Notation!"#
Atomic Mass
Atomic Number(optional)
Element(or Chemical)
Symbol
Examples
11H 42He 23592U
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Isotopes
Nuclide A type of atom characterizedby the number of protons and neutronsin the nucleus of every atom of this type.
Isotopes Atoms with the samenumber of protons (same element) butcontaining different numbers of
neutrons.
Nuclides with same atomic number butdifferent atomic masses.
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238UraniumU
237UraniumU
236UraniumU
235UraniumU
234UraniumU
233UraniumU
232UraniumU
238
92
237
92
236
92
235
92
234
92
233
92
232
92
!
!
!
!
!
!
!Isotopes
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TritiumTorH
DeuteriumDorH
HydrogenH
31
31
2
1
2
1
1
1
Isotopes
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Mass -- Atomic Mass Unit (amu)1 amu = 1/12 mass of Carbon-12 atom
= 1.660565 x 10-27kg
Proton = 1.007276 amu Electron = 0.000549 amu
Neutron = 1.008665 amu
Energy -- Electron Volt (eV)1 eV = 1 electron charge x 1 volt
= 1.60219 x 10-19Joules1 keV = 1,000 eV
1 MeV = 1,000,000 eV
Mass and Energy Units
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The Nucleus Nucleus
Protons & Neutronstightly packed togetherinto a (roughly) spherical
shape.
How Tightly Packed? dnucleus/ datom= 6.4!10-5 Vnucleus/ Vatom= 2.6!10-13
= 0.000000000026%
Image Source: See Note 3
31 pm = 31!10-12m
4He
1.98 fm= 1.98!10-15m
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Nucleus Size Comparisons If atomic volume is the size
of a medium classroom:
30!30!10= 9000 cu. ft.
The nucleus would be thesame size as an a grain ofsand
~8 mils = ~0.2 mm
11
Atomic Diameter = 100 m
Nuclear Diameter = 6.4 mm
Image Sources: See Notes 4 and 5
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1. Public domain:http://en.wikipedia.org/wiki/File:Einstein-formal_portrait-35.jpg
2.
Creative Commons:http://en.wikipedia.org/wiki/File:Atom_diagram.png
3. Creative Commons:http://en.wikipedia.org/wiki/File:Helium_atom_QM.svg
4. GNU license:http://en.wikipedia.org/wiki/File:AmFBfield.svg
5. Creative Commons:http://commons.wikimedia.org/wiki/File:Ballpoint-pen-parts.jpg
Image Source Notes