Transcript 7.4 atomic theory 3

Catalyst – October (4-5+2), 2009
1.
2.
Can people think that theories are
correct even when they are not?
How does this happen?
Do you think that the earth could
be hollow? Why or why not?
Today’s Agenda
Catalyst
 Atomic Theory Part 2
 P.N.E and Atomic Math
 Work Time
 Exit Question

Today’s Objectives
SWBAT describe the evolution of
atomic theory from 1898 to 1932.
 SWBAT locate and describe protons,
neutrons, and electrons in the modern
atom.
 SWBAT do atomic math!

Numero Cinco! - R. A. Millikan
Experiment: Millikan
Oil Drop Experiment
 When: 1909
 Where: U.S.A!!!!

Millikan’s Oil Drop Experiment
Millikan’s Calculations – Whoa!
What were Millikan’s conclusions?
I have most
accurately
measured the
charge of an
electron:
-1.59 x 10-19
Coulombs
What were Millikan’s conclusions?
I have also most
accurately
measured the
mass of an
electron:
9.109 x 10-31kg
Numero Seis! - Ernest Rutherford
Experiment: Gold
Foil Experiment
 When: 1910
 Where: Montreal

http://micro.magnet.fsu.edu/electromag/java/rutherford/
Gold Foil Experiment Explained


Alpha helium particles were shot through a piece of
gold foil
 Think aluminum foil but thinner and made out of
gold!
Alpha helium particles are 8000 times more
massive (bigger) than electrons, so Rutherford
thought they would knock electrons out of the way,
but they did not!
Remember! This is the current model of
the atom (Thanks to Thomson)
More History
Ernie’s (Rutherford) Big Adventure
Thin Sheet of Gold
Atoms
What were Rutherford’s conclusions?
Pretend you are Rutherford
 As Rutherford, what conclusion
would you make based on the
data from the Gold Foil
Experiment?

Hint: Positive repels
positive, negative
repels negative
=
-
+
-
-
-
What were Rutherford’s conclusions?
•Discovered the nucleus, a
concentrated mass with
positive protons!
•Nucleus is in the center of
the atom
•The atom is mostly empty
space
What’s this empty space idea?

The ratio of the size of
the nucleus to the
diameter of the orbits of
electrons can be
compared with placing a
marble in the middle of
a football stadium!
James Chadwick
Experiment – Beryllium
Foil Experiment
 When - 1932
 Where – Cambridge

Conclusions – Neutral
radiation emitted;
therefore, the nucleus
contains another subatomic
particle called the neutron
(has a neutral charge)
PROTON
NUCLEUS
-
-
+
-
+
-
ELECTRON
-
+
+
-
-
-
NEUTRON
Atom Worksheet

Introduce yourself to Mista’ Atom!
Subatomic Particles
Key Point #1: The three main
subatomic particles are…
Protons
Neutrons
Electrons
PROTONS
(purple = positive)
Location: nucleus
-27
Mass: 1.6726 x 10
kg
Charge: 1+

NEUTRONS
(no color = no charge)
Location: nucleus
-27
Mass: 1.6749 x 10
kg
Charge: neutral

ELECTRONS
(in the red = negative)
Location: outside the nucleus
-31 kg
 Mass: 9.1094 x 10
 Charge: 1
The mass of 1,839 ELECTRONS = the
mass of 1 NEUTRON!
Electrons virtually have NO MASS!
Review of Subatomic Particles
Subatomic
Particle
Protons
Neutrons
Electrons
Location
Mass
NUCLEUS
1.6726 x 10-27 kg
NUCLEUS
1.6749 x 10-27 kg
OUTSIDE
NUCLEUS
9.1094 x 10-31 kg
Charge
1+
NEUTRAL
1-
Atomic Math!

Key Point #2: Atomic math
helps us to find…
Number
of protons
Number of neutrons
Number of electrons
This helps us
distinguish
atoms from
each other!
Atomic Math Bylaws
1.
2.
3.
The atomic number of an atom is the same as
the number of ___________________.
PROTONS
The number of electrons is equal to the number
PROTONS
of _______________(in
a neutral atom).
Atomic mass is equal to the number of
PROTONS
_________________
plus the number of
NEUTRONS
_________________.
pREVIEW of the Periodic Table
Atomic Number
Element Symbol
Atomic Mass
Work Time
Complete the Atomic
Structure worksheet
Check your Atomic Math!

Exit Question
1.
2.
What was Rutherford’s contribution to
atomic theory?
Ruthenium has an atomic number of
44. It has an atomic mass of 101.
How many protons, neutrons, electrons
does a neutral atom of Ruthenium
have?