Chapter 5 Quiz - Important People Flashcards
Empedocles
440 BC: stated that all matter was composed of four “elements” (earth, water, air and fire)
Democritus
400 BC: thought that all forms of matter were composed of tiny indivisible particles - “atomos” = “indivisible”
Aristotle
350 BC: supported Empedocles; this theory stuck until the beginning of the 17th century
Dalton
1802: created the billiard ball model of the atom
1. Elements are composed of small indivisible particles called atoms
2. Atoms of the same element are identical in mass (WRONG)
3. Atoms of different elements differ in their mass and size
4. Compounds are formed by combing two or more atoms of different elements
5. Atoms of two elements may combine in different ratios, leading to formation of different compounds
Michael Faraday
(1791-1867)
Discovered that certain substances, when dissolved in water, conduct an electrical current
Noticed that certain compounds decompose into their elements when an electric current is passed through the compound
- atoms of some elements were attracted to the positive electrode, while other atoms were attracted to the negative electrode
= electrically charged!
Named them ions after the Greek term for “wanderer”
Svante Arrhenius
(1859-1927)
Discovered ions (atom/group of atoms carrying a positive or negative charge)
Explained ions + electrical conductivity in ionic compounds!
Discovered cations and anions
G.J. Stoney
(1826-1911)
Discovered and named the electron - decided that there must be some fundamental unit of electricity in these (ions) atoms
No evidence
JJ Thomson
1897
Experimentally proved the existence of the electron with a Crookes Tube
Proposed the Plum Pudding Model
Ernest Rutherford
(1871-1937)
Performed this experiment in 1911 to test the plum pudding model = false
Discovered and proposed the nuclear model of the atom (positively charged nucleus) with electrons floating around it
Goldstein
Discovered the proton
Chadwick
Discovered the neutron
