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Atomic Structure
Elements
Atomic Structure
Matter made of atoms, about 118 elements
(98 naturally occuring).
Number of protons in the nucleus tells you the element (compare Z).
Electrons in "shells" (orbitals) number n = 2•n
2-8-18-32-50
Valence electrons: in the outer most shell.
Give the atom its specific properties.
2
History of the atom - short version
http://en.wikipedia.org/wiki/Democritus
Demokritus (Gr, 400 b.c.): Atamos
John Dalton (Eng, 1766-1844): Atomic theory
J.J. Thomson (Eng, 1856-1940): Electrons
Ernest Rutherford (NZ, 1871-1937): Nucleus
http://en.wikipedia.org/wiki/J._J._Thomson
http://en.wikipedia.org/wiki/Ernest_Rutherford
Groups: same number of valence electrons
(thus alike properties)
Tip! TopDocs: Atom
http://topdocumentaryfilms.com/atom-tim/
Periods: same number of electron shells
Atomic Structure
Particle Relative mass Relative charge
proton 1 +1
electron 0.0005 -1
neutron 1 0
http://www.rum21.se/sv/artiklar/periodiska-systemet-poster-.html
Positive nucleus and negative electrons
Isotope (from greek isos (same) and topos (place), e.i. same place in the periodic table. Same number of protons, but different number of neutrons.
X-notation
http://www.ptable.com/?lang=sv
X
A
Z
A - mass number
Z - atomic number
X - symbol of element
Carbon as an example
Carbon-12: C
Carbon-14: C
12
6
14
6
Carbon-12: 6 protons (thus 6 electrons)
6 neutrons
--------------
12 (=A)
Carbon-14: 6 protons (thus 6 elektrons)
8 neutrons
--------------
14 (=A)
A
Z