Presentation on theme: "It’s time for… THE HISTORY OF THE ATOM Aristotle- ~500 B.C. philosopher What was the world made of? –Water and Earth because it was everywhere –Air because."— Presentation transcript:
Aristotle- ~500 B.C. philosopher What was the world made of? –Water and Earth because it was everywhere –Air because it was around and over us –Fire because it was an agent of change
Democritus 500 B.C. Philosopher Proposed that matter is made of about 100 basic kinds of tiny, indivisible particles he called “atomos.” Nobody believed him. His atoms would look like this:
Who won? Aristotle’s theories could be easily understood The four elements could be easily seen and understood Democritus had no proof fire Smoke =air ashes = earth
400 B.C. - 1500 A.D. The Dark Ages of Chemistry Little research or experimentation done with atoms (or anything else.)
John Dalton - 1803 Experimental Observations - studying gases. CO vs CO 2 Ran electricity through water and…it decomposed! 2 H 2 O --> 2 H 2 + O 2
John Dalton All matter is made of indivisible particles called atoms. All atoms of a given element are identical in mass & properties. Atoms are not created or destroyed - just rearranged in reactions. Different atoms can combine in simple ratios to make compounds. Atoms, according to Dalton: Atoms are all solid with uniform density (like a gum ball)
Cathode ray tube- running electricity through a gaseous element *beam of light” in a was really made of negative particles!
Discovered the electron! Realized that electrons were smaller than atoms. This information discredited part of Dalton’s atomic theory -- Atoms were divisible after all. The atom is made of smaller particles (subatomic particles.)
Plum (electrons) Pudding (positive stuff) Today, it would probably be called the “Chocolate Chip Cookie” Model Thomson’s Model of the Atom:
Ernest Rutherford 1911 Performed the famous gold foil experiment Hypothosis: –If Thomson was correct and atoms contained only diffuse positive charge then… –Most of these heavy positive particles should go right through, right?
Conclusions: Electrons can only exist in certain orbits at a specific distance from the nucleus. Electrons could “jump” to higher orbits (absorbing energy). When they “fell” back down (released energy), they would give off light! If an electron stayed in its orbit, it didn’t lose any energy and would not fall into the nucleus.
Bohr’s Atomic Model: Compares electrons orbiting the nucleus of an atom to planets orbiting around the sun. Electrons occupy distinct orbitals. Orbitals have certain energies and distances from the nucleus. Bohr’s theory explains how light is given off – a huge success!
Erwin Schrodinger 1926 Used mathematical equations to study electrons. Equation gives regions around the nucleus where electrons are likely to be found. Electrons are located in regions called electron clouds. These regions tell us where electrons are most likely to be.
Schrodinger’s Model of the Atom: 2 Parts of the Atom….. Nucleus Electron Cloud Different types of orbitals have different shapes and different levels of energy.