This document provides an overview of the history and development of atomic structure and the atomic model. It discusses early Greek philosophers like Democritus who proposed that all matter is made of invisible indivisible particles called atoms. It then summarizes key discoveries and models proposed by scientists like Dalton, Thomson, Rutherford, Bohr, Schrodinger that refined our understanding of atomic structure, such as discovering the electron, proposing the planetary model of electrons orbiting the nucleus, and the wave mechanical model. The document also defines the basic subatomic particles of protons, neutrons and electrons, isotopes, and provides examples of how atomic mass and ions are related to atomic structure.

1. Today in Science
You will Need:
1)Pencil, Colored Pencils, Highlighters or
Markers
2)Power Notes – Atomic Structure– 1
page 2 sides -Bookshelf
3) DENSITY – Due Now (2pgs 4 sides)

2. Topic:
Power Notes- Atomic
Structure
Do we understand
everything????

3. Democritus 400 BC
Greece - stated that
all matter is made up
of atoms. He also
stated that atoms are
eternal and invisible
and so small that
they can’t be divided,
and they entirely fill
up the space they’re
in
Lavoisier 1789
France - provided the
formula for the
conservation of matter
in chemical reactions,
and also distinguished
between an element
and a compound
• 1st idea of “atoms”
• Believed all matter is made
up of tiny particles separated
by space
• Named particles “atomos”
which means indivisible.
• Founder of modern
chemistry
• 1st carefully controlled
experiments providing
evidence to the Law of
Conservation of Mass

4. Dalton 1766-1844
England - formed the 1st atomic theory,
which states that all matter is composed of
tiny, indestructible particles called atoms
that are all alike and have the same atomic
weight.
1st MODERN Atomic Theory
1.All matter made up of tiny
indivisible particles called atoms
2.Atoms of the same element
have identical properties
3.Atoms of different elements
have different properties
4.Atoms combine in a specific
ratio to form compounds
5.A specific compound is always
made up of atoms in a specific
proportion.

5. Thomson 1897
Plum Pudding Model
1.Negative particles scrambled
into the “dough” of the positive
particles.
England - discovered
the electron and
developed the plumpudding model of the
atom.
Rutherford 1898
England - used the
results of his gold-foil
experiment to state that
all the mass of an
atom was in a small
positively-charged
ball at the center of
the atom.
Gold Foil Experiment
1.Atoms are mostly empty
space
2.All the Mass of an atom is in
the positively charged ball in the
center of the structure.

6. Bohr 1922
Denmark - stated that
the electrons moved
around the nucleus in
successively large
orbits. He also
presented the Bohr
atomic model which
stated that atoms
absorb or emit radiation
only when the electrons
abruptly jump between
allowed, or stationary,
states.
Schrödinger (Schroedinger )
Austria - introduced the
1930
Shroedinger Equation, a
wave equation that
describes the form of the
probability waves that
govern the motion of
small particles and how
these waves are altered
by external influences.
“Planetary” atom model
1.Believed the atom structure was like our
solar system: nucleus in the middle like
the sun and the electrons orbiting like the
planets.
Wave Mechanic Model
1.Planetary model was too specific
2.Rather: electrons vibrate around the
outside of the nucleus- can only
predict where they are most like to be
3.QUARKS – protons, neutrons and
electrons made up of some of these
smaller particles.
4.http://library.thinkquest.org/05aug/01087/quarks.html

7. Basic Atomic Structure
Today scientists agree on the
three basic subatomic particles
that make up all atoms.
Bohr Model for Lithium
Electron = 3
(not to scale)
P= 3 +
N = 3 0
Where is most of the mass in the
Atom?
Where is most of the volume in the
Atom?
NUCLEUS
Outside the Nucleus; Electron
Cloud

8. Nucleus
•
•
•
•
Electron
•
•
•
Contains protons(+) and
Neutrons (0)
Holds most of the mass of
the atom
Very small compared to the
entire size of the atom
Most dense part of the atom
Negatively charged
subatomic particle
Found outside the nucleus in
the electron cloud
Smallest particle; mass =
1/1836th of the atom

9. Proton
•
•
•
•
•
Neutron
•
•
•
•
•
•
Positively charged subatomic particle
Found in the nucleus
Mass = 1 amu (atomic mass unit)
# of protons in an atom IDENTIFIES the
atom (which element)
# of protons in the nucleus of an atom
called the atomic number
Zero charge
Mass = 1 amu
Do NOT affect the identity of the atom
Found in the nucleus
Same atom of an element can have
varying amounts of neutrons (isotope)
Adding the total number of protons &
neutrons = Atomic Mass Number
http://www.sawyerscience.com/Units/unit2/atoms_compounds.html

10. All atoms found on the •
Periodic Table are
Neutral – same # of protons(+) and
# of electrons(-)
Isotope
Atoms of the same element with
same number of protons and
different number of neutrons.
•
nucleus
Hydrogen has 3 natural
occurring ISOTOPES:
Protium, Deuterium and
Tritium
nucleus
Proton
Protiu
m
are
All ROGEN have
l
HYD use al
a
bec oton.
r
1p
nucleus
Tritium
Deuteriu
m
Neutro
n

11. Atomic MASS
IONS
REVIEW & REFLECT
•
On the Periodic Table represents a
weighted average of the mass of all
naturally occurring isotopes of each
element. (based on mass and
abundance of each isotope).
•
When atoms gain or lose electrons
they become charged. (number of
protons (+) and electrons (-)
particles are NOT EQUAL)
+
-

12. Homework
1)None Unless you owe me
something for the 1st quarter report
card
2)3 days left to turn in late or
missing work after today.
Do You see HOW the periodic table
and the Atomic Structure are
RELATED?