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Antoine Lavoisier
Called The Father of Modern Chemistry
Law of Conservation of mass:
- Essential in alchemy and other forms of chemistry
- Discovered when chemical change occurs, the mass at the beginning of the chemical change was equal to the mass at the end of the chemical change.
- The mass of a closed system will remain constant over time
- Mass can neither be created or destroyed -
Marcel Proust
French chemist
Law of definite proportions:
-observed that “specific substances always contain elements in the same ration by mass”
-chemical compounds always contain the same proportions of elements by mass -
John Dalton
Atomic Theory :
a) All matter is made of atoms. Atoms are indivisible and indestructible.
b) All atoms of a given element are identical in mass and properties
c) Compounds are formed by a combination of two or more different kinds of atoms. The ratio of masses of one element that combine with a constant mass of another element can be expressed in small whole numbers.
d) A chemical reaction is a rearrangement of atoms.
Law of Multiple Proportions: -
Gay-Lusssac
Law of combining volumes:
-when two gases react, the volumes of the reactants and products—if gases—are in whole number ratios -
Avogadro
Avogadro’s Hypothesis:
-Two equal volumes of gas, at the same temperature and pressure, contain the same number of molecules
Avogadro's Law:
-At a constant temperature and pressure, the volume of a gas is directly proportional to the number of moles of that gas -
Becquerel
Found that matter containing uranium exposes sealed photographic film
This helped Pierre to find that rays are given off by the elements uranium and radium -
J.J. Thomson
Discovery of the electron:
- believed that the corpuscles emerged from the atoms of the trace gas inside his cathode ray tubes
-atoms were divisible, and that the corpuscles were their building blocks
-corpuscles were distributed in a uniform sea of positive charge
-the electrons were embedded in the positive charge -
Robert Millikan
Accuratly measured the charge on an electron:
- J.J. Thomson discovered the charge-to-mass ratio of the electron
- actual charge and mass values were unknown
-if one of these two values were to be discovered, the other could easily be calculated
-discovered the charge of the electron, which led to the discorvering of the electron's mass by manipulating electrical charges and magnetic fields -
Bohr
Model of the atom:
-called the planetary atomic model
- used evidence of atoms exposed to radiant energy
- when a substance is exposed to a certain intensity of light or some other form of energy, the atoms absorb some of the energy -
Geiger and Marsden
Helped rutherford in his expierements
- subjected a very thin sheet of gold foil to a stream of posivtively-charged subatomic particles
- found that most of the particles passed right through the sheet
- from this rutherford concluded that the atom was mostly empty space -
Planck
Quantum Theory:
- energy is given off in little pockets called quanta
- the amount of energy given off is directly related to the frequency of the light emitted
E=hv -
Pauli
Pauli Exclusion Principle:
- explains the arrangement of electrons
-principle that says no two identical fermions may occupy the same quantum state at the same time
- the total wave function for two identical fermions is anti-symmetric -
Schrödinger
-Austrian physicist who treated electrons as a wave and developed a mathematical equation to descrive it wave-like behavior
-the equation relates the amplitude of the electron wave, to any point in space around the nucleus -
Heisenberg
Heisenberg uncertainty principle:
There is always some uncertainty about the posistion and momentum of an electron
In order to know the position you must first know how much energy it is giving off, and then determine how much velocity it has
Velocity can not be determined so you don't know the position of the electron -
Chadwick
Found high energy particles with no charge and with essentially the same mass as the proton.
Theses are known as neutrons
