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16 Cards in this Set

  • Front
  • Back
very small region located at the center of an atom
negatively charaged particle
positively charged particle
neutral particles
atomic number
number of protons of each atom of that element
atoms of the same element that have different masses
mass number
the total number of protons and neutrons that make up the nucleus of an isoptope
average atomic mass
weighted average of teh atomic masses of the naturally occuring isotopes of an element
Avogadro's number
6.022X10 to the 23 number of particles in exactly one mole of a pure substance
Conservation of Mass
the mass is neihter created or destroyed during ordinary chemical reactions or physical changes
Definite Proportions
chemical compound contains the same elements in exactly the same propotions by mass regardless of the size of the sample or source of the compound
Multiple Proportions
two ro more different compounds are composed of the same two elements, then the ration of the masses of second element combined with a certain mass of the first element is always a ratio of small whole numbers
1. ALl mater is composed of extremely small particles called atoms
2. atoms of a given element are identicl n size, mass, and other properties; atoms of different elements differ in size, mass, and other properties
3. Atoms cannot be subdivided, created, or destroyed
4. Atoms of different elements combine in simple whole number ratios to form chemical compunds
5. In chemical reactions, atoms are combined, seperated, or rearranged
1. Because atoms are electrically neutral, they must contain a positive charge to balance the negative electrons
2. Because eletrons have so much less mass than atoms, atoms must contain other particles that account for most of their mass
oil drop
x-rays to give oil neg charge suspended drops between two charged plates
measured charge of electron
1.6X10 to the neg 19C
Gold foil
all atom's mass was concentrated at a very small, central core of the atom
named the core the nucleus
deduced that the atom was mostly empty space with a dense, central nucleus htat contains positively charged particles held together by nucleur forces