Theory of the Atom

Theory: Explanation based on repeated tests and observations

Philosophy: Study what makes the universe work by using examples and the human mind Science: Study what makes the universe work by observation, experiment and physical proof

Once Upon A Time 440 BC - Democritus “atomos” = indivisible * He also believed that the moon and stars were planets far away from us. p. 80 in text

350 BC Aristotle PhilosopherPhilosopher Tutor to Alexander the GreatTutor to Alexander the Great Everything comes from the 4 elements Earth t Water Fire Wind p. 81 in text

Meanwhile….. Alchemists- tried mixing different materials together to make new things medicine Acids for dissolving things Cleaning chemicals Love potions Magic spells

Meanwhile….. Some alchemists believe in a “Philosopher’s Stone” Transmute – change one material into another Because of the fakers, alchemy became illegal almost everywhere, so they had to “go underground”

Meanwhile….. Alchemists- by doing experiments in which they broke complicated chemicals into simpler ones, discovered different “pure” substances. Pure means these substances are not mixed with something else – ex wood is made of other things and will break down, but Gold cannot be broken into anything simpler.

Meanwhile….. These pure substances become known as “elements”. Alchemists realize that there are actually many elements not just four.

Meanwhile….. Different materials are made by mixing together these elements in certain proportions: Water is H 2 0. It is ALWAYS 2 Hydrogen and 1 Oxygen hooked together.

1803 John Dalton England – Quaker school teacher p. 81 in text Each element is a different kind of “building blocks” atoms

1803 John Dalton p. 81 in text The atoms combine in certain ratios to make new things The Father of Modern Chemistry

1803 John Dalton Atoms are like little billiard balls that stick together or bounce off each other. p. 81 in text

1803 John Dalton Atoms are the smallest particles and cannot be broken into smaller unitsAtoms are the smallest particles and cannot be broken into smaller units Atoms of the same element are the same. Different elements= different kinds of atomsAtoms of the same element are the same. Different elements= different kinds of atoms Atoms join in certain proportions to make new substances.Atoms join in certain proportions to make new substances. p. 81 in text

1897 J J Thomson England Experimented with the cathode ray tube

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1897 J J Thomson England Experimented with the cathode ray tubeExperimented with the cathode ray tube Decided atoms actually have TWO partsDecided atoms actually have TWO parts mostly positive with little negative chunks

1897 J J Thomson England His model for explaining the atom became known asHis model for explaining the atom became known as

1909 Ernie Rutherford from New Zealand Student of ThomsonStudent of Thomson Experiments with new-fangled discovery “radiation”Experiments with new-fangled discovery “radiation” Decides to shoot radiation at Thomson’s puddingDecides to shoot radiation at Thomson’s pudding

1909 Ernie Rutherford If the atom is like pudding, the beam should punch right through Radioactive material Why Gold?

1909 Ernie Rutherford It turned out some of the particles bounced off something

1909 Ernie Rutherford Ernie decided the atom was mostly empty space with the positive part in the center and the negative particles orbiting This is the Solar System Model

1913 Niels Bohr -Denmark Agreed there are + and – particlesAgreed there are + and – particles Proves that – particles actually change paths according to the amount of energy they haveProves that – particles actually change paths according to the amount of energy they have Paths have different shapes, not circlesPaths have different shapes, not circles

1913 Niels Bohr Niels Bohr model Energy Level model

Modern Theory Erwin Schr Ö dinger Werner Heisenberg - particles are so tiny and moving so quickly, we can’t actually predict exactly where they are, only where they are most likely to be.

Modern Theory Erwin Schr Ö dinger Werner Heisenberg

Parts of an atom Positive particles in the center PROTONS Negative particles orbit the center ELECTRONS WHAT HOLDS THEM TOGETHER????

1932 James Chadwick England We can explain that the negative particles stay in orbit because opposites attract

1932 James Chadwick England What keeps the positive particles in the center from flying apart?

Parts of an atom Chadwick used the weights of the atoms to prove there are actually neutral particles between the positive particles

Parts of an atom electrons protons neutrons nucleus This is what you need to know to learn chemistry

Bosons This is what you need to know to learn nuclear physics Quarks electrons P + and n 0 (hadrons)

Bosons electrons P + and n 0 (hadrons) If you are REALLY interested, check out this link!

Parts of an atom electrons protons neutronsQuarks up down charm strange top bottom leptons

Atomic number Element Name Chemical symbol Atomic mass How do I find information about an atom? Use the Periodic Table

Element Name Chemical symbol Atomic mass Atomic number Number of protons in an atom TOTAL number of particles in the nucleus Abbreviation for the element name –may use the LATIN name

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