atomic structure
DESCRIPTION
Atomic Structure. ELEMENTS. 115+ known elements 90 naturally occurring elements 14 most common elements: hydrogen ( H )carbon ( C ) nitrogen ( N )oxygen ( O ) sodium (Na)magnesium (Mg) aluminum (Al)silicon (Si) phosphorous ( P )sulfur ( S ) chlorine (Cl)potassium (K) - PowerPoint PPT PresentationTRANSCRIPT
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Atomic Structure
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ELEMENTS
115+ known elements90 naturally occurring elements
14 most common elements: hydrogen (H) carbon (C) nitrogen (N) oxygen (O) sodium (Na) magnesium (Mg) aluminum (Al) silicon (Si) phosphorous (P) sulfur (S) chlorine (Cl) potassium (K) calcium (Ca) iron (Fe)
CHONPS = elements important for life
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ELEMENTS
all atoms of a specific element have the same number of protons
atoms of different elements have a different number of protons
arranged on Periodic Table to show trends
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PERIODIC TABLE
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ATOMIC SIZE
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SIZE1 mL H2O =
100,000,000,000,000,000,000,000 atoms
1023 atoms …this is more than the number of
drops of water in all lakes, rivers, and streams on Earth
Special microscopes for studying atoms: transmission electron microscope scanning tunneling microscope
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INSIDE AN ATOM
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NUCLEUS
1 millionth of the volume of atom
99.9% of the mass of an atom
very, very dense
contains: protons
neutrons
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PROTON p+
positive (+1) charge
mass = 1.673 x 10-24 g = 1 amu amu = atomic mass unit
all identical
strong nuclear force holds them together
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NEUTRON n0
NO charge
mass = 1 amu
all identical
the number of neutrons can vary for a specific element
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ELECTRON e-
negative (-1) charge
mass = 1/1836 of proton ≈ 0 amuelectron clouds:
space in which e- are likely to be found e- whirl around nucleus billions of times per
second impossible to find the exact position of an
electron more energy means a larger electron cloud
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ATOM vs. ION
ATOM: # of protons = # of electrons NO CHARGE
ION: A charged atom e- < p+ indicates a POSITIVE ION
“CATION” e- > p+ indicates a NEGATIVE ION
“ANION”
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SUBATOMIC PARTICLES
Abbreviation Charge LocationMass
(AMU)
Who?
When?
proton p+ +1 nucleus 1
neutron no 0 nucleus 1
electron e- -1 electron clouds 0
Rutherford
1919
Chadwick
1932
Thomson
1897
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PERIODIC TABLE SYMBOL
Element Name
Atomic Number# of protons
Element Symbol
Atomic Mass (amu)
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ATOM SYMBOL (chromium-52)
Mass Number# protons + # neutrons
Atomic Number# of protons
5224Cr
Element Symbol
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ATOMIC NUMBER
“Z”
number of PROTONS
identifies the element
never, EVER changes for a given element
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MASS NUMBER
“A”
number of PROTONS + NEUTRONS
mass of atom in amu (almost all mass is in the nucleus)
neutrons = mass number –atomic number
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ISOTOPE
atoms of the same element that have different numbers of neutrons (different mass numbers)
similar chemical properties, but different mass
isotopes are named for their mass number, for example:
chlorine-35 35Clchlorine-37 37Cl
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ISOTOPE EXAMPLE
carbon-12: 6 protons 6 neutrons
carbon-14:6 protons8 neutrons
126 C
146 C
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ISOTOPE EXAMPLE
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ION SYMBOL
Mass Number# protons + # neutrons
Atomic Number# of protons
5224Cr
Ion Charge
+2
this atom must have LOST 2 ELECTRONS to become a
+2 ION
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POSITIVE ION CATION
atom that has lost electrons
Protons?
13Neutrons?
14Electrons?
10
2713Al +3
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NEGATIVE ION ANION
atom that has gained extra electrons
Protons?
34Neutrons?
45Electrons?
36
7934Se -2