Download Atoms Intro Notes

Introduction to Atoms
Vocabulary
• Atom• Sub-atomic Particles• Nucleus-
• Atomic Models-
What is an atom?
In this section I want you too…
• Know a general idea of the different models of the
atoms, and why the models have changed over time
• Know what Sub-Atomic Particle each model helped
to explain about an atom
• Be able to draw and label sub-atomic particles and
the atom as we understand it today
Almost all things are MATTER
Matter may consist of elements, compounds, or mixtures.
All matter is made of ATOMS
Atoms are too small to see
This is an image of silicon atoms
arranged on a face of a crystal. It is
impossible to "see" atoms this way using
ordinary light. The image was made by a
Scanning Tunneling Microscope, a
device that "feels" the cloud of electrons
that form the outer surface of atoms,
rather as a phonograph needle feels the
grooves in a record.
Structure of an atom
Atomic Theory Timeline
Democritus vs. Aristotle!
Democritus – 400 BC
Aristotle – 350 BC
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• Continuously divisible
• Everything was apart of an
“elemental”
• More of an alchemist view
Coined Atoms
(ATOMOS = indivisible)
Void space
Solid, card balls
Smallest piece of matter
1808 John Dalton
Dalton thought that atoms were like smooth, hard balls that could not be
broken into smaller pieces.
“Plumb Putting” Model
1897: J.J. Thompson
Thomson suggested that atoms had negatively charged
electrons embedded in a positive sphere.
•Discovered sub-atomic particle called the electron,
Negatively charged particle.
•How discovered?
– Using the cathode ray experiment
1911: Ernest Rutherford
Rutherford was surprised that a few particles were
deflected strongly. This led him to propose an atomic
model with a positively charged nucleus.
•Model points
– Discovered nucleus
– Discovered protons
– Helped to solve the mystery of the charge of the
atom, but not the mass
•How discovered?
– Gold Foil Expirement
1913: Niels Bohr
Through the first part of the twentieth century, atomic
models continued to change. Model points
• Specific orbits around nucleus
• Electrons travel in certain successively larger orbits
• Outer orbits hold more electrons
• Electrons can jump orbits and on way back down,
emit light
Modern Day
Wave Mechanical Model
Summary of BIG IDEAS
• All objects that have mass and take up space are made
of matter
• All matter is made of atoms
• Atoms are made up of positively charged protons and
neutrally charged neutrons. Protons and neutrons stick
together in the nucleus (center) of the atom
• Negatively charged electrons occupy the space around
the nucleus. Electrons move so fast in this space that
they resemble a cloud.
• The space between the nucleus and the electron cloud
is mostly empty
• The model of the atom (what scientists think the atom
looks like) has changed over time because better
technology has allowed us to make better observations
Vocabulary
• Atom• Sub-atomic Particles• Nucleus-
• Atomic Models-
What is an atom?
In this section I want you too…
 Know a general idea of the different models of the
atoms, and why the models have changed over time
 Know what Sub-Atomic Particle each model helped
to explain about an atom
 Be able to draw and label sub-atomic particles and
the atom as we understand it today