This document provides an overview of the history and development of atomic structure theories from ancient Greece to modern times. It discusses key contributors including: - Democritus (400 BC) who first proposed the idea of atoms as tiny indivisible particles. - Dalton (1817-1844) who developed the first modern atomic theory stating that all matter is composed of atoms that combine in specific ratios. - Rutherford (1898) whose gold foil experiment showed that atoms are mostly empty space with a small, dense positively charged nucleus at the center. - Bohr (1922) who proposed the planetary model of electrons orbiting the nucleus like planets around the sun. - Schröding

1. Today in Science
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•Power Notes – Atomic Structure– 2
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2. Topic:
Power Notes- Atomic
Structure
Do we understand
everything????

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

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

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

6. Bohr 1922 Denmark - stated that
“Planetary” atom model
the electrons moved 2.Believed the atom structure was like our
around the nucleus in
successively large solar system: nucleus in the middle like
orbits. He also
presented the Bohr
the sun and the electrons orbiting like the
atomic model which planets.
stated that atoms
absorb or emit radiation
only when the electrons
abruptly jump between
allowed, or stationary,
states.
Schrödinger (Schroedinger ) Wave Mechanic Model
1930 Austria - introduced the •Planetary model was too specific
Shroedinger Equation, a
wave equation that •Rather: electrons vibrate around the
describes the form of the
probability waves that outside of the nucleus- can only
govern the motion of
small particles and how
predict where they are most like to be
these waves are altered •QUARKS – protons, neutrons and
by external influences.
electrons made up of some of these
smaller particles.
•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
(not to scale) Electron = 3
P= 3 +
N = 3 0
Where is most of the mass in the NUCLEUS
Atom?
Where is most of the volume in the Outside the Nucleus; Electron
Atom? Cloud

8. Nucleus • 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
Electron • Negatively charged
subatomic particle
• Found outside the nucleus in
the electron cloud
• Smallest particle; mass =
1/1836th of the atom

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

11. Atomic MASS • 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
IONS
they become charged. (number of
protons (+) and electrons (-)
particles are NOT EQUAL)
REVIEW & REFLECT + -

12. Coloring the Periodic • Outline each box in the following
Table way:
• Metalloids – in BLUE
• Nonmetals – in ORANGE
*Textbook pg 196-197 – Use the • Metals – in GREEN
key

13. Homework
Power Notes– Due by Friday (There
is time to work in class tomorrow)
Do You see HOW the periodic table
and the Atomic Structure are
RELATED?