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Atoms
Physical Science
2015
What does an atom look like?
Atom = smallest complete unit of matter.
Parts of an atom
 Proton
= positively charged
particle located in the nucleus of
an atom
 Neutron = neutral particle located
in the nucleus of an atom
 Electron = negatively charged
particle that orbits the nucleus
Electron Cloud View
Identifying Atoms
 Atomic
symbol = a one or two
letter abbreviation of the element
name
 Atomic number = the number of
protons in its nucleus
 Atomic mass = the average
number of protons and neutrons
in its nucleus
Identifying Atoms
Solving for Neutrons and
Electrons
mass – Atomic number =
# of Neutrons in an atom
 Atomic
 Atomic
# = # of protons = # of
electrons
Isotopes
 Elements
with the same atomic
number but have a different
amount of neutrons (atomic
mass)

This is why atomic mass is usually a
decimal, because it’s an average of
different isotopes
Practice Calculations

What are the
following:







Atomic number
Atomic mass
Atomic Symbol
Name of element
# protons
# electrons
# neutrons
8
O
OXYGEN
16.00
In-Class
Assignment
Do the practice
worksheet and turn in. If
you’re not done, finish for
homework.