What is an atom???
An atom is the smallest particle
of an element that retains its
identity in a chemical reaction.
What are the parts
of the atom???
Positively charged!!
1.) Protons
Neutral
2.) Neutrons
3.) Electrons
Negatively charged
What information do we get
about an atom from the Periodic
Table of Elements?
Mass number
= # of protons
+
# of neutrons
Atomic number
= # of protons
(ID # of an element)
# of protons
= # of electrons
Electron configuration
How many electrons can
you count??
Where are protons, neutrons, &
electrons located in an atom?
• John Dalton’s Model of the Atom:
Atoms are tiny,
indestructible
particles, with no
internal structure.
• J. J. Thomson’s Model of the Atom:
Plum Pudding Model
• Ernest Rutherford’s Model of the Atom:
Rutherford’s Gold Foil Experiment
Ernest Rutherford’s Model of the Atom:
The nucleus is the
tiny, central core of
the atom…contains
protons & neutrons
The electrons are
distributed around
the nucleus and
occupy most of
the volume of the
atom.
• Niels Bohr’s Model of the Atom:
Planetary Model of the Atom
Electrons
move in
circular orbits
at fixed
distances
from the
nucleus.
Given: Mass # = 43
# of electrons = 21
a.) How many protons does this atom have?
# protons = # of electrons
b.) What is the identity of this atom?
# of protons = atomic #
c.) How many neutrons does this atom have?
mass # = # protons + # neutrons