Download The Nature of Science Chapter 1

History of the Atom
Chapter 11
Section 1
Development of the Atomic Theory
Half Full or Half Empty?
Completely Full of Matter!
– Half full of water
– Half full of air
Reminder…
• matter - anything that has mass and takes up
space
– matter is NOT…
• Light, Heat, Emotions, Thoughts, & Ideas
• Matter is made up of
– atoms – the smallest particles into which an element
can be divided and will remain the same substance
• make up elements
• often called the building blocks of matter
Think…
Suppose you cut wood into smaller and smaller
pieces. Do the small pieces seem to be made of
the same matter as the large chunk you started
with?
History of Matter
• Democritus (460 B.C. – 370 B.C.)
– Greek Philosopher
– Thought the universe was made of empty space
and tiny bits of stuff which could not be divided
into smaller pieces
– Named these tiny pieces atoms (Greek word
atomos “indivisible: cannot be divided”)
– Atoms were hard, small particles
– Believed different types of atoms existed for every
type of matter and came in different shapes/sizes
– Ideas were not accepted for nearly 2000 years!
To learn more about something in
science that is too small to be seen,
scientist create…..
MODELS 
History of the Atom
• John Dalton (Early 1800’s)
– Schoolteacher and Chemist
– Atomic Model (Atomic Theory of Matter)
• Set of Ideas (idea model not physical model)
–All substances are made of atoms
–Atoms are small particles that cannot be
created, divided, or destroyed
–Atoms of the same element are exactly alike
–Atoms join with other atoms to make new
substances
History of the Atom
• J.J. Thomson (Late 1800’s to Early 1900’s)
– English Scientist
– Discovered Electrons
• Cathode Ray Tube Experiment
• Atoms were not too tiny to divide
History of the Atom…
• J.J. Thomson (Late 1800’s to Early 1900’s)
– Atomic Model
• Ball of positive charge with electrons embedded in it
History of the Atom
• Rutherford (Early 1900’s)
– British Chemist and Physicist
– Discovered the Nucleus & the Proton (Gold Foil)
– Model of Atom
• Electrons were scattered in the empty space around
the positively charged nucleus.
History of the Atom
• James Chadwick (1930’s)
– Student of Rutherford’s
– Discovered Neutrons: Ran further experiments
using the results of the Gold Foil Experiment
• Found that the particles were heavier because of
Neutrons
– Atomic Model: Proton – Neutron Center
History of the Atom
• Niels Bohr (Early 1900’s)
– Discovered Electron Energy Levels
– Electrons can jump paths/levels
Current Model
• Electron movement is not completely certain
• Electrons stay in the energy levels of the
electron cloud