Download Chapter 4

Chapter 4
Atomic Structure
Section 1- Studying Atoms
• Pg 100-105
• Objectives:
– Describe ancient Greek models of matter
– List the main points of Dalton’s atomic theory
– Describe Dalton’s evidence for the existence of
atoms
– Explain how Thomson and Rutherford used data
from experiments to produce their atomic models
Ancient Greece
• Democritus (~400 BC)
– How many times can you cut
a material in half before you
get to the smallest part?
• Greek word atomos 
uncut or indivisible
• Liquid atoms smooth and
round
• Solid atoms rough and
prickly
• Aristotle thought matter could be divided an
infinite # of times
• Most people agreed with Aristotle rather
than Democritus (until the 1800’s)
Fire
Earth
Air
Water
Dalton
•
•
•
•
Late 1700s
Teacher in England
Studied weather and air (gas)
Determined that gases are made of tiny
particles
• Noticed ratio of masses in a compound
always the same = fixed composition
Dalton’s Atomic Theory
1. All elements are composed of atoms.
2. All atoms of the same element have
the same mass, and atoms of different
elements have different masses.*
3. Compounds contain atoms of more than
one element.
4. In a particular compound, atoms of
different elements always combine in
the same way.
Thomson
• Early 1900s
• Subatomic charged particles
Thomson
• Early 1900s
• Subatomic charged particles
Thomson
•
•
•
•
Early 1900s
Neutral atom
Subatomic charged particles
“plum pudding” model
– Or more modern chocolate chip ice cream
Rutherford
• Early 1900s
• Thomson’s student
• Gold foil experiment
 nucleus
• Positive charge in center, negative on
outside
Rutherford
“It was almost as incredible
as if you fired a 15-inch shell
at a piece of tissue paper and
it came back and hit you.”
Atomic Size
• Figure 8, pg 105
202 ft
• Fieldtrip!
Make a mnemonic!
• Demorcritus’s Blob
• Dalton’s Solid Sphere
• Thomson’s Plum Pudding
• Rutherford’s Positive Nucleus
HW
• Copy and fill in chart in Reading Focus:
Reading Strategy on pg 100.
• Reading checkpoints on pgs 101 & 103.
• Questions in the figures on pgs 101, 102,
105.
• Pg 105 Assessment questions 1-8.
Be prepared for a reading quiz!!!
1.
2.
3.
4.
5.
6.
7.
8.
Pg 105 Answers!
All matter is composed of individual particles called
atoms, which cannot be divided.
Thomson provided the first evidence that atoms are made
from even smaller particles.
All of the positive charge of an atom is concentrated in its
nucleus.
The beam was attracted to a positively charged plate and
repelled by a negatively charged plate
Dalton assumed atoms were solid, indivisible particles.
Thomson had evidence that smaller particles existed
inside atoms.
Dalton had data from experiments to support his theory,
whereas the Greeks did not have data.
The particles have a positive charge.
The nucleus is small compared with the atom as a whole.
Very few of the alpha particles came close enough to a
gold nucleus to be deflected.
Section 4.1 Reading Quiz
Section 2- Atomic Structure
• Pg 108-112
• Objectives:
– Identify three subatomic particles and
compare their properties.
– Distinguish the atomic number of an
element from the mass number of an
isotope, and use these numbers to describe
the structure of atoms.
Discuss Mystery Box
How does your TV work?
• Pg 108, 1st ¶
• Shoot charged particles at the screen
• When the particles of light hit the
screen, the screen lights up for a bit
Subatomic Particles
• Protons
– Rutherford
• Exp. with other materials other than Au
• Amount of positive (+) charge varies in
different elements
• + charge = protons
– Found in the center (nucleus) of atoms
– Assigned charge of +1
– # of protons = atomic number
Subatomic Particles
• Electrons
–
–
–
–
–
Named after Greek word for “amber”
Discovered by Thomson’s experiment
Located outside the nucleus, surrounding it
Assigned charge of -1
Negligible mass
Subatomic Particles
• Neutrons
–
–
–
–
Discovered by James Chadwick in 1932
Neutral = no charge
Found in nucleus with protons
Mass of p+ = mass of no
Proton
Neutron
Electron
Subatomic Particles
and the P.T.
• Atomic # = # of p+
• Atomic mass = # of p+ + # of no
Isotopes
• Same atomic number as the “original”
• Different mass (hence masses aren’t
whole #s)
• Dalton’s 2nd theory
• Ex:
– O-16, O-17, O-18
– H-1, H-2, H-3
– C-12, C-14
Homework!
•
•
Read pgs 108-112
Reading focus
–
–
•
Key Points
Vocabulary
Be able to answer pg 112, 1-9
–
•
Don’t forget Connecting Concepts !
Pay attention to all
1.
2.
3.
4.
Figures
Reading checkpoints
Key points
Anything in bold
Section 3- Modern Atomic
Theory
• Pg 113-118
• Objectives:
– Describe Bohr’s model of the atom and the
evidence for energy levels.
– Explain how the electron cloud model represents
the behavior and locations of electrons in atoms.
– Distinguish the ground state from excited states
of an atom based on electron configurations. (at a
very basic level)
Bohr’s Model of the Atom
• Niels Bohr (1885-1962)
• Danish physicist
• Nobel Prize in 1922
– Atomic structure
– Quantum mechanics
• Manhattan Project
– development of 1st nuclear weapon during
WW II
Bohr’s Model of the Atom
• Where are the electrons?
• Solar system model
Bohr’s Model of the Atom
• e- move in fixed orbitals around the
nucleus
• The amt. of energy an electron has
determines which orbital it will be in
• As an atom gains or loses energy,
electrons can move
Ms. Kramer’s Analogy
The Apartment
32
18
8
2
Ms. Kramer’s Analogy
The Apartment
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
Bohr’s Model
e-
p+ p+ no
o
no no n
p+ o p+
n
e-
e-
e-
Bohr’s Model
ee-
p+ 5
no 6
e-
e-
e-
Bohr’s Model
ee-
p+ 6
no 6
ee-
e-
e-
Bohr’s Model
e-
ee-
p+ 7
no 7
ee-
e-
e-
Bohr’s Model
e-
ee-
p+ 8
no 8
ee-
e-
ee-
Bohr’s Model
e-
ee-
p+ 9
no 10
ee-
e-
e-
ee-
Bohr’s Model
e-
eee-
p+ 10
no 10
ee-
e-
e-
ee-
Bohr’s Model
e-
eee-
p+ 11
no 12
ee-
e-
e-
eee-
Evidence for Energy Levels
• When e- absorb
energy they jump to
higher energy levels
– What state is the
atom in now?
• When e- return to
their original level,
they release energy
– What state is the
atom in now?
– Some energy is
emitted as light
Evidence for Energy Levels
• Side note:
– When the energy gained or lost by an atom is light
energy, each frequency of light corresponds to a
movement of an electron btw 2 energy levels in the
atom. An element can be ID’ed by the frequencies
of light that are absorbed or emitted by its atoms
b/c no 2 elements have the same set of energy
levels. For example, He was discovered on the sun
in 1868 before it was discovered on Earth. The
spectrum of light emitted by gases on the surface
of the sun contained a yellow line that didn’t match
a known element.
Electron Cloud Model
• Electrons are arranged in levels around
the nucleus
– However they do not follow fixed orbitals
• Probability
Flame Test Lab
• Purpose: One sentence, Why are you doing this
lab? Relate your statement to what’s been
covered in class.
• Ex.: Observe the different colors of light
energy released for 9 different elements as
their electrons move from their excited state
down to their ground state.
• Procedure: list, on pg 119 in text
Flame Test Lab
• Data table:
Metal/t.t.#
color
Metal/t.t #
1. boric acid
(boron)
6. lithium
carbonate
2. calcium
carbonate
7. sodium chloride
3. barium
carbonate
8. magnesium
sulfate
4. potassium
chloride
9. copper (II)
sulfate
5. strontium
nitrate
10. hydrochloric
acid
color
Not tested
Flame Test Lab
• Analysis: Identify the unknown.
• Conclusion: Answer “Anaylsis & Conclusion”
questions on pg 119 in text.