Transcript Atom? - Its All about the Science

Physical Science Unit 2 Review
Lesson 1 Atoms
Science Journals
• Get out your science
Journals
• If you don’t have one
use some blank paper
and add it your journal
later
The Development of Atomic Theory
What is an Atom?
• An atom is the smallest
particle that an
element can be divided
and still be that
element.
• For example the smallest
particle of carbon is a
single atom of carbon. If
you divide it is no longer
carbon anymore.
PIECES
OF
CARBON
CARBON
ATOM
What 3 new ideas did John Dalton
propose about the atom?
• All substances are made up of atoms which
are small particles that cannot be created,
divided, or destroyed.
• Atoms of the same element are exactly alike
and atoms of different elements are
different.
• Atoms join with other atoms to form
different substances
J.J. Thomson 1856-1940
• What particle did
Thomson discover? J.J.
Thomson discovered that
atoms are made of
smaller negativelycharged particles called
electrons.
• Thomson’s discovery was
the result of doing
experiments with “cathode
ray tubes”
Ernest Rutherford
(1871 - 1937)
• Awarded the Nobel Prize
in Chemistry for his
discovery of alpha
particles, positively
charged particles emitted
from radioactive elements
• Was a student of J.J.
Thomson but disagreed
with the “Plum Pudding
Model”
• Devised an experiment to
investigate the structure of
positive and negative
charges in the atom.
Rutherford’s Revised Atomic Theory (1911)
Result: Most of the positively charged particles went straight through
the gold foil.
Atomic Theory: Most of the matter of the atom is found in a very small
part of the atom. This is called the nucleus of the atom. It is very tiny
and extremely dense.
Result: Some of the positively charged particles were deflected or even
bounced back.
Atomic Theory: Like charges repel so the nucleus must have a positive
charge. If electrons have a negative charge they could not be in a
positively charged nucleus. Electrons must surround the nucleus at
a distance.
Result: The diameter of the nucleus is 100,000 times smaller than the
diameter of the entire gold atom.
Atomic Theory: Atoms are mostly empty space with a tiny, massive
nucleus at the center .
The Bohr Model of the Atom
What did Bohr learn about electron movement?
• Bohr proposed that
electrons move in paths at
certain distances around
the nucleus.
• Electrons can jump from a
path on one level to a path
on another level.
• Click here
http://www.colorado.edu/p
hysics/2000/quantumzone/
bohr.html
The Modern Theory of the Atom
• Electrons
travel in
regions
called
“electron
clouds”
• You cannot
predict
exactly
where an
electron will
be found
http://www.fearofphysics.com/Atom/atom3.html
Energy Levels
The energy that an electron
has is based on its location
around the nucleus.
(Electrons that are closer to
the nucleus have less
energy than those that are
farther away from the
nucleus)
Lesson 2
• Atoms Number
• Atomic Mass
• Parts of a atom
Subatomic Particles
Particle
Symbol
Charge
Relative
Mass
0
Electron
e-
1-
Proton
p+
+
1
Neutron
n
0
1
Location of Subatomic Particles
10-13 cm
electrons
nucleus
protons
neutrons
10-8 cm
Atomic Number
Atomic Number (Z) of an element is the
number of protons in the nucleus of
each atom of that element.
Element
# of protons
Atomic # (Z)
6
6
Phosphorus
15
15
Gold
79
79
Carbon
Atomic Number on the Periodic
Table
Atomic Number
Symbol
11
Na
16
Learning Check
State the number of protons for atoms of each of
the following:
A. Nitrogen
1) 5 protons
2) 7 protons 3) 14 protons
B. Sulfur
1) 32 protons
2) 16 protons
3) 6 protons
C. Barium
1) 137 protons 2) 81 protons
3) 56 protons
17
Solution
State the number of protons for atoms of each of the
following:
A. Nitrogen
2) 7 protons
B. Sulfur
2) 16 protons
C. Barium
3) 56 protons
19
Number of Electrons
 An atom is neutral
 The net charge is zero
 Number of protons = Number of electrons
 Atomic number = Number of electrons
20
Mass Number
Mass number is the number of protons and neutrons
in the nucleus of an isotope.
Mass number is determined by rounding the atomic
mass to the nearest whole #
16
Arsenic
8
75
Phosphorus
16
8
16
33
75
15
31
Mass # = p+ + no
Lesson 4 Periodic Table
• Since Lesson 3 was a open lesson
Dmitri
Mendeleev
In 1869 he published a table
of the elements organized by
increasing atomic mass.
• http://science.howstuf
fworks.com/periodictable-videosplaylist.htm
1834 1907
How do you read the
PERIODIC TABLE?
How do I find the number of protons,
electrons, and neutrons in an element
using the periodic table?
o # of PROTONS
= ATOMIC NUMBER
o # of ELECTRONS = ATOMIC NUMBER
o # of NEUTRONS = ATOMIC _ ATOMIC
WEIGHT
NUMBER
Lesson 5
• Design of Periodic Table
The horizontal rows of the periodic table
are called PERIODS.
The elements in any group
of the periodic table have
similar physical and chemical
properties!
The vertical columns of the periodic table
are called GROUPS, or FAMILIES.
Lesson 6 Molecules
• Linking atoms together
Atom – the smallest unit of matter “indivisible”
Helium
atom
electron shells
a) Atomic number = number of Electrons
b) Electrons vary in the amount of energy
they possess, and they occur at certain
energy levels or electron shells.
c) Electron shells determine how an atom
behaves when it encounters other atoms
Octet Rule = atoms tend to gain, lose or share electrons so
as to have 8 electrons
C would like to Gain 4 electrons
N would like to Gain 3 electrons
O would like to Gain 2 electrons
Why are electrons important?
1) Elements have different electron
configurations
 different electron configurations mean
different levels of bonding
Electrons are placed in shells
according to rules:
1) The 1st shell can hold up to two electrons,
and each shell thereafter can hold up to 8
electrons.
Lesson 7
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State of Matter
Solid
Liquid
Gas
Any element can be in a different state of
matter depending on the amount of energy.
Lesson 8
• Physical and Chemical Changes
• Physical change is a change in the state of
Matter
• Chemical change is a change in the
molecules to make different molecules.
Examples of Physical Change
• Ice melting
• Kool Aid mixing into water
• Chat some other examples
Chemical changes
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Food cooking
Chemicals the make electricity ie batteries
Metal rusting
Vinegar and baking soda
• Chat me some more examples
Be sure to review notes
• Read over your science journal
• Then complete the review and move on the
Unit Assessment
• We start Unit 3 next week.