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The
Atom
I. Elements
A. Are
• Pure substances
made of only one kind
of atom
An element is a substance made up
of a single type of atom.
I. Elements
B. The Earth’s Ten
Most Abundant
Elements
•
•
•
•
•
O
Si
Al
Fe
Ca
46.6 %
27.7
8.1
5.0
3.6
•
•
•
•
•
Na
K
Mg
Ti
H
2.8 %
2.6
2.1
0.4
0.1
II. THE ATOM
A. What is An Atom?
1. An atom is the smallest particle
of an element that still has the
properties of that element
II. THE ATOM
B. How the Atom was
“Discovered”
1. The Greek
Philosophers
(500 B.C.)
originated the
concept of the
atom.
Atomos =
uncuttable
B. How the Atom was “Discovered”
2. The Dark
Ages
The study of
science was
all but lost
B. How the Atom was
“Discovered”
3. John Dalton (1766-1844)
– Renewed the concept of
the atom
– His model of the atom
resembled that of a billiard
ball - a small, solid sphere
B. How the Atom was “Discovered”
3. John Dalton (1766-1844)
Dalton’s Atomic Theory
• Atoms are indivisible
• Atoms are uniformly dense solid
spheres
• Atoms of the same element are
alike
• Atoms of different elements are
different
B. How the Atom was “Discovered”
4. J.J. Thomson
(1856-1940)
* “Discovered” the electron
• Proposed the “Plum Pudding”
model of the Atom
 Plums = electrons
 Pudding = sea of protons
• Explained the electrical
properties of an atom
B. How the Atom was
“Discovered”
5. Rutherford
(1871-1937)
• discovered the nucleus
• put p+ in the nucleus and the eoutside the nucleus
B. How the Atom was
“Discovered”
5. Bohr
(1885-1962)
• Electrons assume only certain
orbits around the nucleus
like planets around the sun.
• Each orbit has an energy
associated with it.
B. How the Atom was
“Discovered”
6. The Modern
Model
• Quantum Mechanical Model or
• Electron Cloud Model
• Based on a Mathematical
formula
• Predicts where e- are 90% of
time
The cloud
model
represents a
sort of
history of
where the
electron has
probably
been and
where it is
likely to be
going.
III. INSIDE THE ATOM
A. The Nucleus
1.
2.
3.
4.
center of atom
positively charged (+)
gives the atom its mass
contains
• Protons symbol p+
+ chg mass = 1 amu
• Neutrons
0 chg
symbol
o
n
mass = 1 amu
III. INSIDE THE ATOM
B. Energy Levels
1. surround the nucleus
2. negatively charged (-)
3. contains
• Electrons symbol e(-) chg mass = 0 amu
If the proton and neutron were enlarged, and
each had the approximate mass of a
hippopotamus, the electron, enlarged to the
same scale, would have less mass than an
owl.
III. INSIDE THE ATOM
C. Atoms are Electrically Neutral
1. # protons = # electrons
2. Example:
+
Sodium has 11 p
-11 etotal charge 0
REVIEW IT NOW!
Complete the chart below:
Particle Symbol
Proton
Neutron
Electron
Mass
Chg
Location
REVIEW IT NOW!
Particle Symbol
Proton
Neutron
Electron
+
p
Mass
Chg
Location
REVIEW IT NOW!
Particle Symbol
Mass
Proton
1
amu
Neutron
Electron
+
p
Chg
Location
REVIEW IT NOW!
Particle Symbol
Mass
Chg
Proton
1
amu
+1
Neutron
Electron
+
p
Location
REVIEW IT NOW!
Particle Symbol
Mass
Chg
Proton
1
amu
+1 Nucleus
Neutron
Electron
+
p
Location
REVIEW IT NOW!
Particle Symbol
Mass
Chg
Proton
+
p
1
amu
+1 Nucleus
Neutron
n0
Electron
Location
REVIEW IT NOW!
Particle Symbol
Mass
Chg
Proton
+
p
+1 Nucleus
Neutron
n0
1
amu
1
amu
Electron
Location
REVIEW IT NOW!
Particle Symbol
Mass
Chg
Proton
+
p
+1 Nucleus
Neutron
n0
1
amu
1
amu
Electron
0
Location
REVIEW IT NOW!
Particle Symbol
Mass
Chg
Proton
+
p
+1 Nucleus
Neutron
n0
1
amu
1
amu
Electron
0
Location
Nucleus
REVIEW IT NOW!
Particle Symbol
Mass
Chg
Proton
+
p
+1 Nucleus
Neutron
n0
1
amu
1
amu
Electron
e-
0
Location
Nucleus
REVIEW IT NOW!
Particle Symbol
Mass
Chg
Proton
+
p
+1 Nucleus
Neutron
n0
Electron
e-
1
amu
1
amu
0
amu
0
Location
Nucleus
REVIEW IT NOW!
Particle Symbol
Mass
Chg
Proton
+
p
+1 Nucleus
Neutron
n0
Electron
e-
1
amu
1
amu
0
amu
0
-1
Location
Nucleus
REVIEW IT NOW!
Particle Symbol
Mass
Chg
Location
Proton
+
p
+1 Nucleus
Neutron
n0
Electron
e-
1
amu
1
amu
0
amu
0
Nucleus
-1
Around
nucleus
III. INSIDE THE ATOM
D. Quarks
1. Protons and neutrons are made of smaller
particles called quarks
• Up quarks and Down quarks
• Quarks are held together by gluons
2. Electrons are not made of smaller particles
d
u
d
u
u
d
d
u
d
u
u
d
u
IV. Atomic Number, Mass Number and
Isotopes
A. Atomic Number
1. Is the number of protons
2. # protons determines the
identity of the atom
3. Remember
#
+
p
=#
e
4. You can get # p+ from the
periodic table
11
Atomic
Number
Na
Atomic
Symbol
Sodium
Atomic
Name
22.990
Atomic
Mass
(Average)
B. Mass Number
1.Mass Number
= Protons + Neutrons
2. Examples
Sodium
# protons =
11
# neutrons = 12
mass number =
?3
2
B. Mass Number
2. Examples
Boron
atomic number =
mass number =
5
11
number of neutrons = ?6
YOUR TURN:
1. WHAT ELEMENT
IS THIS AN
ATOM OF?
2. WHAT IS THE
ATOMIC
NUMBER OF
THIS ATOM
3. WHAT IS THE
MASS NUMBER
OF THIS ATOM?
1. Sc
2. 21
3. 45
YOUR TURN:
4. WHAT ELEMENT
IS THIS AN
ATOM OF?
5. WHAT IS THE
ATOMIC
NUMBER OF
THIS ATOM
6. WHAT IS THE
MASS NUMBER
OF THIS ATOM?
4. K
5. 19
6. 39
YOUR TURN:
7. WHAT ELEMENT
IS THIS AN
ATOM OF?
8. WHAT IS THE
ATOMIC
NUMBER OF
THIS ATOM
9. WHAT IS THE
MASS NUMBER
OF THIS ATOM?
7. Cs
8. 55
9. 133
YOUR TURN
COMPLETE THE CHART
#P
25
#E
25
F
?9
9
9
?
18
Al
13
?
13
?
14
27
K
?
19
19
?
20
39
Mn
# N MASS #
30
?
55
The Atomic Mass on the
Periodic Table is the Average
Mass – If you round the mass
number to a whole number
then you can calculate the # of
neutrons in the most common
atoms of the element.
Ex. Na = 22.990
Determine the following
about the most common
atom of gold:
Au
A. Symbol
79
B. Atomic Number
197
C. Mass Number
79
D. Number of Protons
E. Number of Electrons 79
F. Number of Neutrons 118
C. Isotopes
1. Are atoms of the same element
with different numbers of
neutrons
2.Example
– Some atoms of boron have 6
neutrons. What is the mass # ?
11
C. Isotopes
2.Example
– Some boron atoms have 5
neutrons. What is the mass #?
10
Check Your Understanding
– Atom A has 15 protons and 17
neutrons
– Atom B has 18 protons and 17
neutrons
Are the atoms isotopes or are
they atoms of different
elements?
different elements
C. Isotopes
3. Names and Symbols of Isotopes
Include the element name or
symbol and mass #
• Example
Some atoms of boron have 6
neutrons. What is the name and
symbol of this isotope?
Boron 11
11B
5
D. 3 Laws of Chemistry
A. The Law of the Conservation of
Mass
In any chemical reaction, matter
(and therefore mass) is neither
created or destroyed.
D. 3 Laws of Chemistry
A. The Law Definite Proportions
In any like chemical compound,
atoms always combine in definite
proportions.
ex. molecules of water always contain
2 hydrogen atoms and 1 oxygen
atom
D. 3 Laws of Chemistry
A. The Law Multiple Proportions
Atoms can combine in different
ratios to create different
compounds.
ex. H2O is water, H2O2 is hydrogen
peroxide
WHAT DO WE MEAN BY
RADIOACTIVITY?
Radioactive decay is the process in which an unstable
atomic nucleus loses energy by emitting radiation in
the form of particles or electromagnetic waves.
There are numerous types of radioactive decay. The
general idea:
An unstable nucleus releases energy to
become more stable
SCIENCE PARK HS -- HONORS CHEMISTRY
FISSION – THE SPLITTING OF A NUCLEUS TO
RELEASE ENERGY
FUSION – THE COMBINING OF TWO NUCLEI TO
RELEASE ENERGY
SOME KEY DEFINITIONS BEFORE
WE
MOVE
ON
Z = The Atomic Number. It’s the Number of Protons
in the nucleus of an Atom.
Nucleus: It’s where the Protons and Neutrons are
located in an Atom.
Protons: Positively Charged Particles in the Nucleus
of the atom. Mass = (approx) 1 AMU
Neutrons: Neutrally charged particles in the nucleus
of an atom Mass = (approx) 1 AMU
Mass Number of an atom: Number of Protons +
Number of Neutrons in the nucleus of an atom.
SCIENCE PARK HS -- HONORS CHEMISTRY
THREE COMMON TYPES OF
RADIOACTIVE EMISSIONS
Alpha
Beta
Gamma
SCIENCE PARK HS -- HONORS CHEMISTRY
THREE COMMON TYPES OF
RADIOACTIVE EMISSIONS PENETRABILITY
Alpha particles may be
completely stopped by a
sheet of paper, beta
particles by aluminum
shielding. Gamma rays,
however, can only be
reduced by much more
substantial obstacles, such
as a very thick piece of
lead.
SCIENCE PARK HS -- HONORS CHEMISTRY