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Fundamental Atomic Particles
Part 1Atomic Structure
Standard Atomic NotationIsotopes
Isotopic Abundance
Learning GoalsStudents will be able to:understand standard atomic notationexplain the relationship between the atomic
number and the mass number of an element, and the difference between isotopes and radioisotopes of an element
identify the scientists who contributed to the development of the modern Periodic Table
Success CriteriaStudents will be able to:writing radioactive decay equationsdetermining the number of protons, neutrons
and electrons in an atom.explaining the contributions of scientists who
developed the modern Periodic TableCalculate average atomic abundance using
isotopic abundance values
Review of Atomic Structure
Atomic Theory andThe Periodic TableReview the development of atomic theory:Read pages 14-16 for Mendeleev and DöbereinerRead pages 24-25 for Bohr and RutherfordRead page 27 for SoddyReview the information on the various
groups within the periodic table.Read pages 10-11 for basic Chemistry term and
Information on the elementsRead pages 17-19 on the groups within the
periodic table
Modern View of Atomic StructureThe atom has 2 main regions
a) Nucleus - protons and neutronsb) Electron cloud- region where you might find an electron
Rutherford’s Gold Foil experiment (remember grade 9) proved that the atom has an extremely dense, heavy nucleus surrounded by mostly empty space (save for some very light electrons).
Rutherford’s Gold Foil Experiment
The Gold Foil Experiment
The Gold Foil ExperimentThe gold foil is only
a few atoms thick.Most of the
positively charged α-particles pass straight through the gold foil
A few are deflected the tiny positively charged nuclei of the gold atoms
Density and the AtomSince most of the α-particles went through
the gold atoms in the thin gold foil, it proved that the atom was mostly composed of empty space.
Since alpha particles are positively charged (they are actually the nuclei of helium atoms), they must be deflected by a positively charged “nucleus”.
Since so few of the α-particles were deflected, the nucleus must be very small
This nucleus was determined to contain almost all of the atoms mass.
Size of an atomAtoms are small.
Measured in picometers, 10-12 metersHydrogen atoms have a 32 pm radiusIF the atom was the size of a stadium, the nucleus
would be the size of a marble.Hence most of an atom is empty space – thus you
are mostly made out of nothing.
Radius of the nucleus near 10-15m.
The density of the nucleus is near 1014 g/cm3
A dice made of a nucleus would weigh 100,000,000 tonnes (this equals 1000 supertankers).
Subatomic particles
ElectronProtonNeutron
Name
Symbol
Charge
Relative mass
Actual mass (g)
e-
p+
n0
-1+10
1/184or ≈ 0
1
1
9.11 x 10-
28
1.67 x 10-
241.67 x 10-
24
Standard Atomic Notation
Contain the symbol of the element (X), the mass number (A) and the atomic number (Z)
Xmass number (A)
atomic number (Z)
elementsymbol
12
Standard Atomic NotationRemember from grade 9:1) Symbol• 1 or 2 letter - the first is always a capitol• the symbols of many elements come from their
latin roots (ex. Gold (Au = aurum))2) Atomic Number• the number of protons in the nucleus (atom)3) Mass Number• the mass of the atom - since almost all of the
mass comes from the nucleus;• mass number = number of protons + number of
neutrons
Standard Atomic Notationthe area to the top right
of the symbol is used for ionic charge
the area to the bottom right of the symbol is used for number of atoms (ex. H2)
Standard Atomic NotationFIND THE NUMBER OF PROTONS,
NEUTRONS AND ELECTRONS FOR AN ATOM
1) Protons = atomic number2) Electrons = atomic number unless
an ionic charge is indicated (remember a positive charge indicates that electrons were LOST)
3) Neutrons = atomic mass - atomic number (can you explain this?)
Find the number of protons, neutrons and electrons for the two atoms at left
SymbolsFind the
number of protonsnumber of neutrons
number of electrons
atomic numbermass number
F19 9
16
Symbols Find the
number of protonsnumber of neutrons
number of electrons
atomic numbermass Number
Br80 35
17
Symbols If an element has an atomic
number of 34 and a mass number of 78 what is the number of protonsnumber of neutronsnumber of electrons standard atomic notation
18
Symbols If an element has 91 protons
and 140 neutrons and an ionic charge of what is the atomic numbermass numbernumber of electronscomplete symbol
19
Isotopes
IsotopesSoddy determined that atoms of the same
element can have different numbers of neutronsThis means that an element can have different
mass numbersSoddy called these atoms isotopes.Carbon has 3 isotopes, only 1 is common.
Naming IsotopesPut the mass number after the name of the
elementcarbon- 12 or C-12carbon -14 or C-14uranium-235 or U-235http://www.youtube.com/watch?v=EboWeWm
h5Pg (Tyler DeWitt _ Isotopes)
http://www.youtube.com/watch?v=n4WZ0-fItt8 (Tyler DeWitt – Isotopes and Elements examples)
Isotopes and Atomic MassFor example magnesium has 3 naturally occurring
isotopes with masses of 24, 25 and 26.What atomic mass should be placed in the periodic
table?
Scientists decided that the average weight of the atoms based on the abundance should be placed on the periodic table as the atomic mass.
This explains why mass values have decimals.http://www.youtube.com/watch?v=dRfrvpVdKGM (Tyler
DeWitt)
Determining Isotopic AbundanceThe Mass Spectrometer
Determining Isotopic Abundanceof Magnesium
Determining Isotopic AbundanceThe Mass Spectrometer
Mass Spectrometer scan of a protein found in a performance enhancing drug at the Olympics.
Mass Spectrometer read-out of Magnesium isotopes.
Try these questionsCalculate the relative atomic mass of gallium given that
the relative abundance of its two isotopes are: 60.5% of Ga-69 and 39.5% of Ga-71.
Iron has four isotopes; Fe-54 (5.82%); Fe-56 (91.66%); Fe-57 (2.19%) and Fe-58 (0.33%). Determine the average atomic mass for natural iron.
Magnesium has three isotopes. 78.99% magnesium 24 with a mass of 23.9850 amu, 10.00% magnesium 25 with a mass of 24.9858 amu, and the rest magnesium 25 with a mass of 25.9826 amu. What is the atomic mass of magnesium? (note the more accurate data)
If not told otherwise, the mass of the isotope is the mass number in amu (atomic mass units)
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