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Studying AtomsStudying Atoms
•Ancient Greek ModelsAncient Greek Models
•Dalton’s TheoryDalton’s Theory
•Thomson’s ModelThomson’s Model
•Rutherford’s TheoryRutherford’s Theory
Ancient Greek ModelsAncient Greek Models
• Atoms cannot be seen even with a microscope
• Atomos in Greek means uncut
• Democritus- the smallest indivisible particle of matter is an atom
Dalton’s TheoryDalton’s Theory
• The ratio’s of the masses in a compound are constant
• Dalton proposed the theory that all matter is made up of individual particles called atoms
• All elements are composed of atoms
• All atoms of the same element have the same mass
• Compounds contain atoms of more than one element
• Atoms in a particular compound always combine in the same way
Dalton’s TheoryDalton’s Theory
Thomson’s ModelThomson’s Model• Charges attract or repel• - like charges repel, • -opposite charges attract• Thomson was able to bend a
beam of charged particles using a magnet
• His experiments provided the first evidence of subatomic particles
• Chocolate chip model of an atom- although neutral Thomson’s experiment displayed charges in atoms.
• The chocolate chips represent the negative portion of an atom and the surrounding the positive portion- the cookie
Thomson’s ModelThomson’s Model Thomson model
Rutherford’s Atomic TheoryRutherford’s Atomic Theory
• Alpha particles are positively charge particles
• Using gold foil he found that particles where deflected differently than expected
• Positive charge in an atom concentrated in central area called the nucleus
• The relative size of the nucleus would equal the size of a marble in the center of a football field
Rutherford’s Atomic TheoryRutherford’s Atomic Theory