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400
demoritus
proposed the matter formed small peacies can't cut smaller parts. chase determined the properties of substanses. combined term atoms contrd to divied atom can no be divied anymore. -
400
aristotle 400 bc
started all substances are madeof 4 elements- Earth 2.water 3.fire 4, air
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John Dalton
John Dalton transformed Demoucritus ideas on atoms into a mordern atomic moldel. 1] all matter is made of tiny microscopic particals called atoms.
2] the atoms the same elements are identical thoes of different elements are compounds.
3] atoms of different elements combine in small, whole number ratioe to form compound.
4]chemical reactoins involve the combonations of atoms no new atoms are created [ law of simple multiple prop] -
j.j Thompson
Discovered the elctron contucted cath ode ray tube.
by adding an positive charge he found ot the moving particals were oppisite. -
robert mililikan
determined the mass and charge of electron. cunducted oil experiment. from the mass of a drop and the charge on the plates he calculated the chage on a electron. -
ernest rutherford
discovered the gold flod experiment
. the nucleus is made up of mostley charge and mass
.nthe atoms catains a posittive peace of center. -
nelis Bohr
propesed that an electron is founnd only in pecific circular paths pr orbit around the nuculeus. bohr model Refered to as plantetarymodel because electrons move around the nuctenus like planrts around the sun. -
sir james chadwick
comfirmined the existence of nectoty in the nucules the atoms is mostely electrons space
the cosits of 2 regions.
nucleus in the center it contains protons and newtrons .