S.MORRIS 2006
Study of matter- 2000 years ago!!
Aristotle and Democritus were 2 Greek
philosophers who gave us some basic
ideas. Aristotle- four elements- Earth,
air, fire, water!!
Democritus- if you keep cutting matter
into smaller pieces, you can eventually
cut no more- this INDESTRUCTIBLE
INDIVISIBLE piece is called ATOMOS
(meaning indivisible in Greek)
HISTORY OF THE ATOM
John “4 Good Ideas” DALTON
Matter is made up of tiny spheres.
Dalton named them: ATOMS
(atomos term
given by Democritus)
Dalton’s 5 ideas about “ATOMS”:
1. Everything is made of atoms
2. All atoms of the same element are identical
3. Atoms of different elements are different
4. Atoms can team up to make compounds
5. Atoms can’t be broken into smaller parts
HISTORY OF THE ATOM
Joseph “I shall name you ELECTRON!!”
Thomson
Found that atoms could
sometimes eject a really
small negative particle which
he called an
ELECTRON
JUST LISTEN: JT’s Experiment
• Put + and –
plates near
“laser” and
it was
attracted to
the positive.
• What
charge was
the stream
of the
laser?
Thomson’s (wrong) “PLUM PUDDING”
MODEL IDEA:
Thought atoms were filled with a positively
charge goo that balanced the electron’s
negative charge (wrong!)
 like plums
surrounded by pudding
Ernest “IT’S A NUCLEUS!” Rutherford
Shot helium atoms at a piece of gold
foil which was a few atoms thick.
About 1 in 10,000 bounced off
something in the gold foil!
Ernest “It’s a nucleus!” Rutherford
helium nuclei
gold foil
helium nuclei
A few of the helium atoms bounced off something.
Helium Nuclei
Helium Nuclei
If the “Plum
Pudding” model
were true.
Gold foil!
The actual
result: some
bounced back
like they hit
something
solid!
“Nucleus” Rutherford’s gold foil evidence
showed him atoms have a nucleus in the center.
He determined that the nucleus had a positive
charge, and that the negative electrons were
attracted to the positive nucleus.
However, this was not the end of the story…
Niels “Orbits” Bohr
• Bohr figured out that the electrons were in
orbits (like planets orbiting the sun).
• Each orbit holds a set number of electrons.
Bohr’s thinking
•Noticed that
elements absorbed
and emitted the
same colors.
•Concluded
electrons absorb
energy to “jump” up
levels and lose the
same energy when
they “fall” back
down.
James “I shall call you NEUTRON!” Chadwick
• Shot radiation into wax. Saw:
1) Radiation didn’t bend toward + or –
plates, so neutrons must have no
charge (neutral).
2) The radiation made atoms eject a
proton—so this particle must have
mass too!
• He named the particle the
NEUTRON.
Just Listen: Jimmy’s Experiment
• Because the radiation forced
protons out of the atoms, the
radiation was made of heavy
particles! Neutrons have mass!
Build a MNEMONIC!
•
•
•
•
•
D ogs
T urn
R owdy
By
C lapping
The Current Model of the Atom
• Electron Cloud Model:
– Nucleus: p+ and no
– Electron cloud: surrounded by e- that
move so fast they look like a blur (think
fan blades)
•E- are more likely
found closer rather
than farther away
Guiding questions:
• Who discovered which parts of the atom?
• In what order were the things discovered?
ATOM (Dalton) with ELECTRONS (Thomson)
in ORBITS (Bohr)
Orbit/
proton
Shell
+
electron
N
N
+
-
neutron
Atomic Structure: Where do they live?
Protons (p+): In nucleus.
Neutrons (n0): In nucleus with protons.
Electrons (e-): outside nucleus, zooming around
SUBATOMIC PARTICLE CHARGE AND MASS:
Particle
Charge
Mass
proton
Positive
1
neutron
No charge
1
electron
Negative
0
Mass is measured in Atomic Mass Units (AMUs)
Positive Proton
Neutral Neutron
(negative electron: e- )
Flag Practice: Charges, Masses,
Location
Guiding Questions
• What are the three parts of the atom?
• Where are the subatomic particles
located?
• What are the charges of the subatomic
particles?
• What are the masses of the subatomic
particles?
Purpose of Subatomic Particles
• Different amounts of protons change what
atom it is.
• Different amounts of neutrons make atoms
unstable and radioactive (they shoot
particles out!)
– Isotopes: atoms with different amounts
of neutrons.
• Different amounts of electrons make
atoms have different charges.
– Ions: atoms with a charge (+ or -)
Atoms are neutral
ATOMS ARE NEUTRAL
• If atoms are neutral,
the number of
positive protons
must be ___?___
the number of
negative electrons
ATOMS ARE
NEUTRAL!!!!
The # of P = The # of e-
The # of e- = the # of p
ATOMIC STRUCTURE
He
2
4
 Atomic Number
The # of protons in an
atom
 Atomic Mass
The # of protons +
neutrons in an atom
number of protons = number of electrons.
Why??
Mr. Addem Proneumass
Get it??? Add them…Addem….
Pro + Neu = Mass
The Atomic Mass
• The Atomic Mass must be rounded
because there are different isotopes of
every atom.
• Every isotope has a different mass and is
present in different amounts on the earth.
• To calculate the atomic mass, we consider
how much each isotope weighs and which
form is most common on the earth.
– Ex: Atomic Mass of Boron = 10.81 AMU.
– How many neutrons on average?
Let’s Label our Periodic Table!
• Find hydrogen.
• Circle the atomic number.
• Put a rectangle around the atomic mass.
What is hydrogen’s…
atomic number
atomic mass
# of p
# of e
# of n
Make the following table in your notes…
Symbol Atomic Atomic # of p+
#
Mass
Au
Ca
F
Na
Rn
Pb
K
# of e-
# of n0
Homework Activity
• Spell out a message or phrase to your assigned
partner.
• Create an answer key to give to me (name,
A.M., A.N., P, e-, N for each element)
Assigned partner has to find:
• The element name
• Atomic Mass for each element
• Atomic Number for each element
• P, N, and e-
Atomic Mass vs Number Homework
•
•
•
•
Worksheet
Worksheet
And worksheet some more
RAFT activity? Or a raft after
configuration notes?
QUIZ
GUIDING QUESTIONS
• How is atomic mass calculated?
How do you get the atomic number?
• Why must the number of protons and
electrons be equal?
ATOMIC STRUCTURE
Electrons are arranged in Energy Levels
(a.k.a Shells/Orbits) around the nucleus
(Bohr’s idea!)
•1st shell
max of 2 electrons
•2nd shell
max of 8 electrons
•3rd shell
max of 8 electrons
(Sneak Preview)
• The electrons in the outermost shell are
called “valence electrons” and are super
important for determining how atoms
bond.
• Way more important than regular
electrons.
• WAY MORE.
Bohr DIAGRAMS
Elements are represented by Dots or Crosses
to show electrons, and circles to show the
shells (orbits) of electrons
X
Nitrogen
X X
N
XX
X X
N
7
14
Bohr DIAGRAMS
Draw the Bohr diagrams for the following elements;
a)
O
8
b)
16
X
X
X
X
X
O
X Cl X
X
X
X
X
X
X
X
X
35
X
X
X
X
X
Cl
X
17
X
X
X
X
X
SUMMARY:
1. The Atomic Number of an atom = number of
protons in the nucleus.
2. The number of Protons = Number of e2. The Atomic Mass of an atom = number of
Protons + Neutrons in the nucleus.
4.
Electrons orbit the nucleus in shells.
5.
Each shell carries a set number of e-’s
Symbols
•
•
•
•
•
•
•
•
Hydrogen
Helium
Lithium
Mercury
Lead
Carbon
Nitrogen
Oxygen
H
He
Li
Hg
Pb
C
N
O
Symbols
•
•
•
•
•
•
•
•
Fluorine
Neon
Sodium
Magnesium
Gold
Tin
Iodine
Aluminium
F
Ne
Na
Mg
Au
Sn
I
Al
Symbols
•
•
•
•
•
•
•
•
Sulfur
Silicon
Phosphorus
Chlorine
Potassium
Calcium
Iron
Copper
S
Si
P
Cl
K
Ca
Fe
Cu
Symbols
•
•
•
•
•
•
Cobalt
Nickel
Zinc
Arsenic
Silver
Radon
Co
Ni
Zn
As
Ag
Rn