Chem

Front 1

nucleus

Back 1

very small region located at the center of an atom

Front 2

electron

Back 2

negatively charaged particle

Front 3

proton

Back 3

positively charged particle

Front 4

neutron

Back 4

neutral particles

Front 5

atomic number

Back 5

number of protons of each atom of that element

Front 6

isotope

Back 6

atoms of the same element that have different masses

Front 7

mass number

Back 7

the total number of protons and neutrons that make up the nucleus of an isoptope

Front 8

average atomic mass

Back 8

weighted average of teh atomic masses of the naturally occuring isotopes of an element

Front 9

Avogadro's number

Back 9

6.022X10 to the 23 number of particles in exactly one mole of a pure substance

Front 10

Conservation of Mass

Back 10

the mass is neihter created or destroyed during ordinary chemical reactions or physical changes

Front 11

Definite Proportions

Back 11

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

Front 12

Multiple Proportions

Back 12

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

Front 13

Dalton

Back 13

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

Front 14

Thomson

Back 14

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

Front 15

Milikan

Back 15

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

Front 16

Rutherford

Back 16

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