Transcript CP Chemistry Chapter 4 - Barnegat Township School District

Honors Chemistry Chapter 4
The Structure of the
Atom
Early Theories of Matter
•Atomic Theory
–Democritus
–Dalton
Dalton’s Atomic Theory
• Based on experimental results
• Matter consists of atoms
• All the atoms of an element are alike
• Atoms of one element differ from atoms of
other elements
• Atoms are indestructible and only
rearranged during chemical reactions
• Atoms can combine in simple, wholenumber ratios to form compounds
• Pg. 102
Discovery of the electron
• Cathode ray tube (Crooke’s
tube)
• Pg. 105 picture
• Cathode rays
–Particles with negative
charge
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JJ Thompson
Used cathode ray tube to
determine charge/mass ratio of
particles
Identified the particles as
electrons
Robert Millikan

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Calculated the charge and mass of an
electron
“Oil drop” experiment
Electron carries exactly one unit of
negative charge
Mass is 1/1840 the mass of a hydrogen
atom
• Each electron carries one unit of
negative charge
• Proposed “plum pudding” model of
the atom
• “chocolate chip cookie” model
• Electrons stuck in positive “dough”
Rutherford’s Gold Foil
Experiment
pg.
107
IMPORTANT RESULTS!!!!

New atomic model
• Atom mostly empty space
• Tiny, dense central core –
nucleus

Rutherford's gold foil experiment

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Contains all the atoms positive
charge
Volume of space in which the
electrons move huge compared to
volume of the nucleus
 Book
analogy:
 If an atom had a diameter of
2 football fields, the nucleus
would be the size of a nickel!
Don’t you wish you were
here right now?
WELL
YOU’RE NOT –
SO PAY
ATTENTION!!!!!!!!!!!!!!!!!
!!!!

Atomic Theory song!!!
NUCLEONS – particles
located within the nucleus
Protons and neutrons
Protons
 Positive
charge
 Mass of 1 amu (atomic
mass unit)
Neutrons
–No charge (neutral)
–Mass = 1 amu
Electrons
Located outside the nucleus in
“shells”
 Each carries one unit of negative
charge
 Mass 1/1840 amu


Pg. 106 chart for subatomic
particles
Atomic number
Number of protons in the nucleus
Identifies the atom as an atom of a
particular element
Determines its position on the
Periodic Table
Atomic # = #protons = #electrons
MASS NUMBER
Number of protons + number of
neutrons
 Number of neutrons =
mass number – atomic number

Isotopes
Isotope Notation

Pg. 112 Sample and practice
Average atomic mass
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Weighted average of the naturally
occurring isotopes of that element
Is a decimal because of the existence of
isotopes
Pg. 114 Table 4.3
Pg. 116-117 #21-24
Video: How to Calculate an Average
Atomic Weight.
Periodic Table
Arrangement of elements where
the elements are separated into
groups bases on a set of repeating
properties
 Can compare properties of
elements based on their position
on the table

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Arranged according to increasing atomic
number
Horizontal rows – periods
Vertical columns – groups (families)
• Elements within a group have similar
chemical and physical properties