-
200
about 400 B.C
another greek man named democruitus said that matter was made up of tiny particles that can not be broken down any more -
300
about 350 B.C.
the philosopher aristotle belived the four element model and the writings were so great that it was accepted for 2000 years. -
400
500-1600 A.D.
alchemists belived that metal was made like plants for many of years but then they made chemical symbols for each kind of metal and now there called elements. -
500
1650
a english scientists robery boyle made a new definition for the word element and it was a pure substance that can not be broken down into simpler substances. -
Mar 26, 600
late 1700s
joseph priestly was man that isolated oxygen scientifically but did not know that oxygen was a element. Than antoine lavoiser experimented with priestleys oxygen, lavoiser concluded that air must be a mixture at least two gases one which of oxygen. -
Mar 26, 700
1808
John Dolton publishes a theory why elements differ from each other and from non elements. daltons atomic model from matter was.
all matter is made of atoms. which are particles to small to see.
each element has its own kind of atom with its own particular mass.
compounds are created when atoms of different elements link to form molecules.
atoms cannot be created, destroyes or subdivided in chemical changes . -
Mar 26, 1000
1911
Ernest rutherford designed a experiment to test thomson's and nagaoka's models. he aimed for a type of radiation called alpha particles, a type of particle smaller than most atoms.based on thomson's raisinbun model that the particles would pass straight through the gold foil. most of them did but a small amount bounced back almost straight from the gold foil.because of that Rutherford made a new model called the nuclear model -
About 450 B.C.
a greek man named empedocles found out that matter was composed of four elements earth, air, fire and water. He found out that each of these elements mixed in different porportions to make different substances. -
1904
J.J thomson made the discovery of very light nagitive particles and also found much heavier particles. the new model came known as the raisinbun model.
a japenese scientist H.nagaoka working about the same time modelled the atom as a large shpere surrounded by a ring of negitive electrons. -
1800s
in 1831 micheal faraday found that electric current may cause chemic changes in some compounds in solution. the atoms may gain electric charges and form charged atoms called ions. he made a modified version of daltons model which was,
matter must contaiin postitve and negitive charges
opposite charges attract and like charges repel.
atoms combine to form molecules because of electrical attrections between atoms.
