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