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31 Cards in this Set

  • Front
  • Back
all matter can be broken down into __
# of elements, # of natural elements
114, 88
3 facts known by chemists in the 18th century
1. materials were mixtures of pure substances
2. pure substances are elements or compounds
3. law of constant composition
dalton's atomic theory
1. elements made of atoms
2. atoms in an element are identical
3. atoms of different elements are different from each other
4. compounds always have the same relative #s and types of atoms
5. atoms cant be divided in a chemical process
compound is a...
distinct substance composed of atoms of two or more elements

relative mass is always the same
chemical formula is..
notation for describing the type and number of atoms in a unit (molecule) of a given compound
rules for writing a chemical formula
1. each atoms is represented by a chemical symbol

2. the number of each type of atom is indicated by a subscript

3. 1 atom present means 1 subscript
H2o (ex.)
a molecule consisting of 2 hydrogen atoms for every 1 oxygen atom
a molecule with 1 sulfur atom for every three oxygen atoms
atom is composed of 3 particles...
who discovered the electron
JJ Thompson
who proposed the plum pudding model
William Thompson
who discovered the proton
Ernest Rutherford
what did the discovery of the proton do
disproved the plum pudding model
led to the development of the nuclear atom
who discovered the neutron
James Chadwick
what does the atom look like and composed of
positively charged nucleus surrounded by negatively charged electrons

nucleus (+)
electrons (-)
what does the nucleus look like
has positively charged protons
electrically charged neutral neutrons

protons (+)
neutrons (neutral)
how big is the necleus
.00000000001 cm. (diameter)
how is the atom charged electrically
number of protons and electrons are the same
where is the mass of an atom contained
electron (relative mass and relative charge)
relative mass 1
relative charge (-1)
proton (relative mass and relative charge)
relative mass 1836
relative charge +1
neutron (relative mass and relative charge)
relative mass 1839
relative charge none
atoms with same number of protons but different number of neutrons
atomic number
number of protons in the nucleus

mass number
sum of the number of protons and the number of neutrons in the nucleus

notation for an isotope

(mass number)
chemical symbol
(atomic number)
periodic table first arranged by
Dmitri Mendeleev
metals have physical properties like...
1. good conductor of heat and electricity

2. malleability (hammered into thin sheets)

3. ductility (can be pulled into wires)

4. a lustrous apperance (shiny)
noble metals (unreactive)
diatomic molecules
made up of 2 atoms of the elements

ex. O2 (oxygen gas)
N2 (nitrogen gas)
H2 (hydrogen gas)