Download The Structure of the Atom

The Structure of the
Atom
Chap. 4
I. History
I. History
A. Early Greeks
Explain matter with 4 ‘elements’
I. History
A. Early Greeks
1.
2.
3.
4.
Air
Earth
Fire
Water
Explain matter with 4 ‘elements’
I. History
A. Early Greeks
B. Democritus
Greek philosopher who first
introduced concept of ‘atomos’
I. History
A. Early Greeks
B. Democritus
C. Alchemists
Devoted to making precious
metals from base metals
I. History
A.
B.
C.
D.
Early Greeks
Democritus
Alchemists
Dalton
Formulated the ‘Atomic Theory
of Matter’
Atomic Theory of Matter
1. All matter is made of . . .
Atomic Theory of Matter
1. All matter is made of . . .
2. Atoms cannot be . . .
Atomic Theory of Matter
1. All matter is made of . . .
2. Atoms cannot be . . .
3. Atoms of a given element . . .
Atomic Theory of Matter
1.
2.
3.
4.
All matter is made of . . .
Atoms cannot be . . .
Atoms of a given element . . .
Atoms of 2 different elements . .
Atomic Theory of Matter
1.
2.
3.
4.
5.
All matter is made of . . .
Atoms cannot be . . .
Atoms of a given element . . .
Atoms of different elements . . .
In a chemical reaction atoms are
I. History
A.
B.
C.
D.
E.
Early Greeks
Democritus
Alchemists
Dalton
Definition of Atom
Atom
The smallest particle of an
element that retains
properties of that element.
II. Discoveries of atoms
A. J.J. Thomson – 1890s
Used a cathode ray tube (CRT)
to measure the charge:mass
ratio of an electron
II. Discoveries of atoms
A. J.J. Thomson – 1890s
1. chg:mass =
11
1.76 x 10 C/kg
II. Discoveries of atoms
A. J.J. Thomson – 1890s
1. chg:mass =
11
1.76 x 10 C/kg
2. Discovery led to
plum-pudding model
II. Discoveries of atoms
A. J.J. Thomson – 1890s
B. Robert Millikan - 1909
Measured the charge of an
electron in his ‘oil drop’ exper.
II. Discoveries of atoms
A. J.J. Thomson – 1890s
B. Robert Millikan - 1909
1. Charge = 1.6 x 10-19
II. Discoveries of atoms
A. J.J. Thomson – 1890s
B. Robert Millikan - 1909
C. Rutherford - 1911
Discovered nucleus in gold-foil
experiment
II. Discoveries of atoms
A. J.J. Thomson – 1890s
B. Robert Millikan - 1909
C. Rutherford - 1911
1. Fired alpha particles at thin
metal sheet.
II. Discoveries of atoms
A. J.J. Thomson – 1890s
B. Robert Millikan - 1909
C. Rutherford - 1911
1. Fired alpha particles at thin
metal sheet.
2. Expected them to go straight
through, but some deflected.
II. Discoveries of atoms
A. J.J. Thomson – 1890s
B. Robert Millikan - 1909
C. Rutherford - 1911
1. Fired alpha particles at thin
metal sheet.
2. Expected them to go straight
through, but some deflected.
3. This led to nuclear model.
II. Discoveries of atoms
D. The atom
II. Discoveries of atoms
D. The atom
1. The electron was
discovered first
II. Discoveries of atoms
D. The atom
1. The electron was
discovered first
2. The proton was described
by Rutherford
II. Discoveries of atoms
D. The atom
1. The electron was
discovered first
2. The proton was described
by Rutherford
3. The neutron was described
by Chadwick
III. Representing Atoms
What makes a carbon atom
different from a nitrogen atom?
III. Representing Atoms
A. The atomic number
III. Representing Atoms
A. The atomic number
1. The number of protons
III. Representing Atoms
A. The atomic number
1. The number of protons
2. Written on the periodic
table.
III. Representing Atoms
A. The atomic number
1. The number of protons
2. Written on the periodic
table.
3. This will equal the number
of electrons, too.
III. Representing Atoms
A. The atomic number
B. The mass number
III. Representing Atoms
A. The atomic number
B. The mass number
1. The number of protons +
neutrons
III. Representing Atoms
A. The atomic number
B. The mass number
1. The number of protons +
neutrons
2. Always a whole number
III. Representing Atoms
A. The atomic number
B. The mass number
C. Isotopes
III. Representing Atoms
A. The atomic number
B. The mass number
C. Isotopes
1. Atoms with the same
number of protons, different
number of neutrons
III. Representing Atoms
A. The atomic number
B. The mass number
C. Isotopes
1. Atoms with the same
number of protons, different
number of neutrons
2. Isotopes have same
properties, but different
masses
III. Representing Atoms
A.
B.
C.
D.
The atomic number
The mass number
Isotopes
Notation
Nuclide Symbol Notation
37
17
Cl
Nuclide Symbol Notation
Element symbol
37
17
Cl
Nuclide Symbol Notation
37
17
Atomic number
Cl
Nuclide Symbol Notation
Mass number
37
17
Cl
Self Check – Ex. 1
Write the nuclide symbols
for elements with these
particles:
Nuclide #1
22 protons
24 neutrons
Nuclide #2
22 protons
26 neutrons
Self Check – Ex. 2
How many protons,
neutrons, and electrons are
in this element?
95
42
Mo
Self Check – Ex. 3
How many protons,
neutrons, and electrons are
in this element?
40
K
IV. Mass of atoms
IV. Mass of atoms
A. Measured in amu
IV. Mass of atoms
A. Measured in amu
B. Protons and neutrons both
weigh about 1 amu
(neutrons are a bit more)
IV. Mass of atoms
A. Measured in amu
B. Protons and neutrons both
weigh about 1 amu
(neutrons are a bit more)
C. The amu is defined as 1/12
the mass of carbon-12
V. Atomic Mass
V. Atomic Mass
A. A weighted average of all
the isotopes for a given
element
An analogy
The older pennies have a mass of 3.0 g
while the newer pennies have mass of
2.5 g. What is the average mass of these
pennies?
An analogy
The older pennies have a mass of 3.0 g
while the newer pennies have mass of
2.5 g. What is the average mass of these
pennies?
5
older
5
newer
An analogy
What is the average mass of this
sample? There are 4 older pennies
(3.0 g) while there are 10 newer
pennies have mass of 2.5 g.
4 older
10
newer
An analogy
The older pennies have a mass of 3.0 g
while the newer pennies have mass of
2.5 g. What is the average mass of these
pennies?
older
newer
V. Atomic Mass
A. A weighted average of all
the isotopes for a given
element
B. Formula
Atomic Mass
% Isotope #1 x Mass of isotope #1
+
% Isotope #2 x Mass of isotope #2
+
% Isotope #3 x Mass of isotope #3
+
=
all other isotopes
Atomic mass
Self Check – Ex. 4
Use the following to find the
atomic mass for chlorine.
Chlorine-35
75.53 %
34.969 amu
Chlorine-37
24.47 %
36.966 amu
VI. Radioactive Decay
VI. Radioactive Decay
A. Some atoms spontaneously
emit radiation
VI. Radioactive Decay
A. Some atoms spontaneously
emit radiation
B. Atoms change their
identities in the process
VI. Radioactive Decay
A. Some atoms spontaneously
emit radiation
B. Atoms change their
identities in the process
C. Atoms undergo radioactive
decay because their nuclei
are unstable
VII. Types of Radiation
VII. Types of Radiation
A. Alpha radiation
VII. Types of Radiation
A. Alpha radiation
1. Make unstable heavy nuclei
lighter
VII. Types of Radiation
A. Alpha radiation
1. Make unstable heavy nuclei
lighter
2. This radiation is attracted to
negative electric fields
VII. Types of Radiation
A. Alpha radiation
1. Make unstable heavy nuclei
lighter
2. This radiation is attracted to
negative electric fields
3. Comprised of alpha particles
Alpha Particles
Made of: 2 protons & 2 neutrons
Charge:
Mass:
Symbol:
Alpha Particles
Made of: 2 protons & 2 neutrons
Charge: 2 +
Mass:
Symbol:
Alpha Particles
Made of: 2 protons & 2 neutrons
Charge: 2 +
Mass: 4 amu
Symbol:
Alpha Particles
Made of: 2 protons & 2 neutrons
Charge: 2 +
Mass: 4 amu
Symbol:
4
2
He or
4
2
α
VII. Types of Radiation
B. Beta radiation
VII. Types of Radiation
B. Beta radiation
1. Increases the proton to
neutron ratio
VII. Types of Radiation
B. Beta radiation
1. Increases the proton to
neutron ratio
2. Radiation is attracted to
positive electric field
VII. Types of Radiation
B. Beta radiation
1. Increases the proton to
neutron ratio
2. Radiation is attracted to
positive electric field
3. Comprised of beta particles
Beta Particles
Made of: An electron from the
nucleus
Charge:
Mass:
Symbol:
Beta Particles
Made of: An electron from the
nucleus
Charge: 1 -
Mass:
Symbol:
Beta Particles
Made of: An electron from the
nucleus
Charge: 1 -
Mass: 1/1840 amu
Symbol:
Beta Particles
Made of: An electron from the
nucleus
Charge: 1 -
Mass: 1/1840 amu
Symbol:
0
-1
e-
or
0
-1
β
VII. Types of Radiation
C. Gamma radiation
VII. Types of Radiation
C. Gamma radiation
1. These accompany alpha and
beta radiation
VII. Types of Radiation
C. Gamma radiation
1. These accompany alpha and
beta radiation
2. Not deflected by electric field
VII. Types of Radiation
C. Gamma radiation
1. These accompany alpha and
beta radiation
2. Not deflected by electric field
3. Gamma rays are high energy
radiation
Gamma Particles
Made of: Energy (not matter)
Charge: none
Mass: none
Symbol:
0
0
γ
VIII. Penetrating Ability
VIII. Penetrating Ability
A. Alpha radiation penetrates
the
.
VIII. Penetrating Ability
A. Alpha radiation penetrates
the least.
B. Gamma radiation
penetrates the
.
VIII. Penetrating Ability
A. Alpha radiation penetrates
the least.
B. Gamma radiation
penetrates the most.
IX. Writing Equations
IX. Writing Equations
A. Atomic numbers and mass
numbers are conserved
IX. Writing Equations
A. Atomic numbers and mass
numbers are conserved
B. Examples
Self Check – Ex. 5
Complete the following
nuclear equation.
40
19
K
40
20
Ca + ?
Self Check – Ex. 6
Complete the following
nuclear equation.
239
94
Pu
? + α
4
2