

negatively charged particles with a mass of
0.0006 a.m.u. (or just put zero) that equal the
# of positive protons in the nucleus
their exact location around the nucleus is
not known--Heisenberg’s uncertainty
principle.


an electrons’s position, momentum, or energy can
never be precisely determined
measuring any variable disturbs the others in an
unpredictable way

therefore, we say they are found in an electron
cloud or orbital


electron orbitals represent a volume of space
where an electron would have a 95% probability
of being found
many orbitals can make up an electron level

as electrons are added to an atom, they settle into
the lowest unfilled energy level

for this class (Physical Science), each level or
orbit, can only hold a certain amount of
electrons




1st → up to 2 electrons
2nd → up to 8 electrons
3rd → up to 8 electrons
4th → up to 8 electrons
 (really 18)


the properties of elements depends on how
many electrons are in a particular atom’s
different levels
valence electrons are the electrons in the very
last or outermost energy level

draw a sodium atom

and a chlorine atom

Draw a aluminum atom

valence electrons are represented as dots
around the chemical symbol for the element
Na
Cl

Draw the following atoms (Mr. J uses the light
table and draws with students)