Download Atomic Theories

Atomic Theories
Did Dan just realize
beryllium’s metal?
What did the element say when
he got into a fight?
Let me atom
Democritus
• Greek philosopher
• the originator of a theory on
atoms
• He said atoms are the smallest
indivisible bodies from which
everything else is composed
Dalton
• Developed the first useful atomic
theory
• His theory was comprised of 4
postulates
The postulates
1. All matter consists of tiny
particles called atoms
2. Atoms are neither created
nor destroyed (based on???)
The postulates (cont.)
3. All atoms of a given element
are identical and different
from any other element
4. A given compound always
has the same relative
numbers and kinds of atoms
J.J. Thomson
• Discovered that the atom has a
substructure using a cathode
ray
• Discovered a negatively
charged particle and named it
the electron
Cont.
• Couldn’t calculate the mass
of an electron but figured out
the ratio of its charge to its
mass
T-money cont.
• His model is called the mint choc.
chip model because
• The atom was electrons
surrounded by a soup of positive
charge to balance the electron's
negative charge, like chips
surrounded by mint ice cream.
Ernest Rutherford
• Performed the gold foil experiment
to discover the positively charged
nucleus
• He shot a beam of alpha particles at
a piece of gold foil, while most went
through, there were some that got
scattered in every direction
• Pg. 104
Are you Bohr’d yet?
• Niels Bohr’s model depicts the
atom as a small, positively charged
nucleus surrounded by electrons
that travel in circular orbits around
the nucleus
• Improvement on Rutherford's model
Modern Atomic Theory
• Nucleus lies in the center of the
atom
• Electrons do not orbit in welldefined paths, rather they can
be predicted in an area called an
electron cloud
Something to break the monotony
• When they broke open
molecules, they found they
were only stuffed with atoms.
But when they broke open
atoms, they found them
stuffed with explosions.
Subatomic Particles
ProtonNeutron-
ELECTRON-
Proton
• positive
• found in the nucleus
• has the mass of 1 amu
Joke 1
• A Hydrogen atom runs up to two other
atoms yelling and waving his arms. "Help!
A mugger just stole my electron!" One of
the other atoms looks him over and asks,
"Are you sure?" The first replies: "I'm
positive!"
Neutron
• Neutral
• found in the nucleus
• has the mass of 1 amu
Joke 2
• A neutron walks into a bar and
orders a drink. When he
attempts to pay, the bartender
looks at him and says, "For you,
no charge."
ELECTRON
• Negative
• found outside the nucleus
• its mass is so small comparably
that it is considered negligible
Joke 3
• SUBATOMIC PARTICLE STORE
The subatomic particle store had a
sale last week.
Electrons: $0.10
Protons: $0.10
Neutrons : free of charge
Atomic Number
• # of protons
• Atoms are neutral so the # of
protons must equal ________
• The whole number found in
the element box
Atomic Mass
• Number of protons + number
of neutrons
• Measured in AMUs (Atomic
mass units)
• Where are the electrons?
Isotopes
• Atoms that have the same
number of protons but different
number of neutrons
• Do isotopes have the same
charge?
• Do isotopes have the same
masses?
Isotope notation
Isotope Notation decoded
• "X" represents the atom's
elemental symbol.
• "A“--The mass number, (located in
the upper left-hand corner)
• "Z“-- The atomic number (found
in the lower left-hand corner)
Last joke
• Q: What did the
thermometer say to the
graduated cylinder?
• A: "You may have graduated
but I've got many degrees"