Chapter 3: Atoms, the Building Blocks of Matter

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Chapter 3 Atoms, the Building Blocks of Matter
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Atomic Theory has Evolved!

• Leave a couple of lines!

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Law of Conservation of Mass

• Mass is neither created nor destroyed during an
  ordinary chemical reaction or physical change.
• Remember the Candle Lab
• C25H52 O2 E CO2 H2O C
  E

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Draw a picture and explain why it happens?

• Leave about a half a page for an activity

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Pioneers of the Atomic TheoryChapter 3

• Observant people have been looking at matter and
  pondering why different phenomenon occur for
  hundreds of years.

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Early Philosophers- Aristotle and Democritus

• Didnt agree!!

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Dead Dude 1- Democritus

• Ancient philosopher- 460BC
• Matter is made of indivisible particles.
• Atomos means that which cannot be further broken
  down

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Shortcomings

• It is a conceptual definition, not based on
  science.
• Doesnt talk about subatomic particles.

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Dead Dude2- DaltonExplained the Laws

• John Dalton (early 1800s)
• Atom is a solid, indestructible mass (like a
  billiard ball)

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All Atomic Theory builds on Daltons Law

• All matter is made of tiny particles called
  atoms.
• All atoms of a given element are identical in
  size, mass and properties Atoms of each element
  are different.
• Atoms cannot be subdivided, created or destroyed.
  
• 4. Compounds consist of atoms of different
  elements combined together. Compounds have
  constant composition (fixed ratio of atoms).
• 5 Chemical reactions involve the rearrangement
  of those atoms.

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Dead Dude 3

• J.J Thomson- 1850
• A ball of positive mass containing a number of
  electrons that are embedded.
• Getting the idea that there are protons and
  electrons (nucleus).

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Shortcomings

• Doesnt explain the existence of electrons
  outside the nucleus or their importance in
  bonding.
• No neutrons- cant explain radioactivity or the
  existence of isotopes.

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What did experiments with the cathode ray tubes
teach us?
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Late 1800s

• Discovery of and experiments using the cathode
  ray tube led to our understanding of the
  electron.

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Millikan Oil Drop Experiment
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Henri Becquerel- 1897

• Researched newly discovered X-rays
  (Phosphorescence).
• Accidently discovered that uranium emits
  radiation that could be measured using
  photographic plates.
• Discovered Radioactivity- electrically charged
  particles.

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The Drs Curie- 1898

• Discovered new elements- Polonium and Radium.
• Very unstable elements that give off energy.
• This led to an under- standing of Alpha, Beta and
  Gamma particles.

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Dead Dude 4

• Rutherford Model- 1905
• Mass of the atom is concentrated in the center of
  a positively charged region called the nucleus.
• The Planetary Model

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Gold Foil Experiment- Draw this and leave some
room to write about the experiment.
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Shortcomings

• Doesnt place the electrons.
• Doesnt include neutrons.

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Bohr Model-1920

• Believed that electrons traveled in precise
  orbits around the nucleus of an atom

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Schrodinger Quantum Mechanical Model.

• Describes mathematically the wave properties of
  electrons and other very small particles

• The nucleus is at the center of the atom and the
  electrons are in the electron cloud.