Download Unit 2 Part 1 History of the Atom

Unit 2 Part 1
History of the Atom
Ms. Slack
6th Grade Science
2010
Lets Review…
What is MATTER?
• Matter is anything that has mass and
takes up space!
• What is NOT considered matter?
• Light, Heat, Emotions, Thoughts
• Everything around us is either classified
as matter or energy.
What Makes up Matter?
• Democritus (460 BC – 370 BC):
– Greek philosopher
• believed that the universe was made up of empty space
• bits of ‘stuff’ that were so small they could no longer be
divided.
– He called these tiny pieces atoms
– Greek word which means ‘cannot be divided
• Today an atom is defined as a small particle
that makes up most types of matter.
Other Early Contributions
• Lavoisier was a French chemist who lived
about 2000 years after Democritis.
• Before Lavoisier, people thought that matter
could appear and re-appear. Example?
• Wood burning in a fireplace.
Law of Conservation of Matter
• Matter is not created or destroyed, it
just changes form.
Models of the Atom
• Models are often used for things that are too
small or too large to be observed.
• In the case of atoms, scientists use large
models to explain something that is too small
to be looked at.
• Atoms are so small they cannot be seen with
the human eye.
ATOMIC THEORY TIMELINE
The Scientists and History of the
Atomic Theory and Models
John Dalton – early 1800’s
His ideas included:
1. All matter was made up of one type of
atom.
2. Atoms are too small to see with the
“naked” eye.
J.J. Thomson Model
He discovered:
1. Atoms can be divided into “subatomic” or
smaller particles.
2. Discovered the electron!
Envisioned an atom to look like a:
ball of chocolate chip cookie dough
or a blueberry muffin
Rutherford Model 1910
Rutherford discovered:
1. The atom is mostly empty
space.
2. Has a positively charged
center called the “nucleus”.
3. Called the positively charged
parts “protons!”
Chadwick Model –
1930’s
A student of Rutherford’s
he discovered:
1. The “neutron” – a
particle in the nucleus
with NO CHARGE!
Modern Atomic
Model
The current model includes the following:
1. Electrons have energy levels – from low to
high.
2. Electrons are found in a cloud “circling” around
the nucleus.