HOW ATOMS DIFFERStart with some Vocab• Atomic Number
• Atoms total # of Protons
• Atoms Total # of Electrons
Note: as long as the atom is neutral in charge
• Atomic # identifies an atom of a particular element.• It never changes
How to read the Periodic Table
CHECK• Identify the following to fill in the chart.1. Name of element2. # of Protons3. Average Atomic Mass
ATOMIC NUMBERSComplete the following tableComposition of Several Elements
Element Atomic Number Protons Electro
nsa. Pb 82b. 8c. 30
82 82
Zn 30 308 8O
ISOTOPES AND MASS NUMBER• What do we know…?• Does the # of protons of
an element ever Change?• NO
• Does the # of electrons of an element ever change?• NO
• What’s Left?• # of Neutrons will
change
• What does this mean?
Atoms with the same number of protons but
different number of neutrons are called
isotopes.
THE MASS NUMBERSo…The Mass Number is…(Atomic #) + (# of neutrons)
What makes up the mass number of an isotope.• Remember Relative
Mass• Protons = 1amu• Neutrons = 1amuWhat’s this mean? • If an element has 1
proton and 1 neutron what's the Mass Number?• 2
WHAT DOES ALL THIS MEAN?Elements have different forms in nature• Lets look at Copper…• How many protons in Copper?
• 29 protons• Does this ever change?
No• But copper has two forms with different mass
numbers.• What changes…# of Protons or # of Neutrons?
# of neutrons
COPPER - ISOTOPESCopper – 63Copper - 65Other ways to write it
Mass number
Cu65
29Cu63
29
Other ways to write it
LEARNING CHECK• 1st… J.J. Thomson• The Plum pudding Model…didn’t last long• We know…Atoms are neutral / no charge (positives
cancel negatives)• Proposed…Uniformly (evenly) distributed positive and
negative charges.
LET’S PROVE THE NUCLEUS• Didn’t happen…• The alpha particles (positive charge) bounced all over
the place…Why?
LET’S PROVE THE NUCLEUS• The Protons have a positive charge…repelled the
positive alpha particle• The neutron has no charge doesn’t effect it.
THE MASS OF THE ATOM
What does relative mean?• Comparative / in proportion to
something• So…whats
1.67x10-27
1.67x10-27= 1 (relative)
ONE LAST NOTE
• Quarks? And plasm?• Parts that make up
Protons and neutrons• Scientists don’t know
their effect on chemical behavior
Top Related