Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
6 Cards in this Set
- Front
- Back
|
ANCIENT GREEKS |
The Greeks 450 to 350 B.C.E. -Before common era They thought that all matter was made of the four “elements”: Fire, Air, Earth & Water. Everything on earth was a combination of these four things. |
|
|
JOHN DALTON |
John Dalton (An English School teacher and a Chemist) 1800s He suggested all matter is made up of Particles that could not be divided. He called the particles Atoms. Believed that each element has its Own Unique Properties. When the atoms combine, they make New Substances. Billiard Ball Model could not be divided any smaller. Thomson made up the “Plum-Pudding” model of the atom. Atoms are made up of positive charges and electrons all Mixed Together In A Sphere. |
|
|
WILLIAM CROOKS and J.J. THOMSON |
William Crooks and J.J. Thomson Late 1800s Invented the Cathode Ray Tube. When he put electricity through the gas in the tube, it gave off a Green Light. Thomson found that this light could be Deflected By A Magnet. Thomson said that atoms must have Negatively Charged Particles. That meant that there must also be a Positive Charge In The Atom. |
|
|
ERNEST RUTHERFORD |
Rutherfords Gold Foil Experiment 1911 He was testing Thomson’s model of the atom. He shone very tiny, high speed particles (called Alpha Particles) through a piece of Thin Gold Foil. He thought that the particles were so tiny that they would Pass Straight Through the foil. Most of the particles did, but some Deflected. They must have hit something hard in the atom. Rutherford decided that the atoms must contain A Very Small Central Portion Surrounded By A Lot Of Space. Rutherford said that atoms contain a Tiny, But Very Massive nucleus, made up of positively charged protons, surrounded by a Cloud Of Electrons. |
|
|
NEILS BOHR |
Bohr and Flames Tests Early 1900s Neils Bohr studied the element hydrogen. When he added energy, the atoms always gave off the same 4 Colours Of Light. Each element has its own Line Spectrum(like a light fingerprint) light. Bohr realized that the light was given off when the electrons were given energy and got excited. When the electrons Return To Their Non-excited State(ground state), they give off this energy as Light.Bohr realized that the electrons were not it clouds around the nucleus, they were in “Orbits”, just like the planets orbit the sun. |
|
|
JAMES CHADWICK |
Chadwick and the Neutron 1932 A third particle in the atom was found, called the Neutron. It is found in the Nucleus and has No Electrical Charge. This is the model of the atom that we still use today. |
