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The Atom
What is
Matter?
• anything that has
________ and
takes up ________
• matter is made up
of ________
(2 Volunteers)
How Small are Atoms?
• It would take a stack of about 50,000 aluminum atoms
to equal the thickness of a sheet of aluminum foil from
your kitchen
• If you could enlarge a penny until it was as wide as
the US, each of its atoms would be only about 3 cm in
diameter – about the size of a ping pong ball
• A human hair is about 1 million carbon atoms wide
• A typical human cell contains roughly 1 trillion atoms
• A speck of dust might contain 3x1012 (3 trillion) atoms
• It would take you around 500 years to count the
number of atoms in a grain of salt
Activity:
• Rip or cut a standard piece of paper in half as
many times as you can.
Class Discussion:
• How many cuts were we able to make? ____
• Do you think we could keep cutting the paper
forever? Why or why not?
• You would have to cut the paper in half
around thirty-one (31) times to get to the size
of any atom.
What is an Atom?
• the smallest unit into which matter
can be ____________________
• ___________________________
of all matter
• comprised of a
________________(at it’s center)
and an
___________________________
(surrounding the nucleus)
• made up of ___________ _particles
What are Subatomic
Particles?
• smaller than an atom
• __________________
• __________________
• __________________
Early Atom Models:
What is the
Rutherford Model?
• mostly empty
• small, positively (+)
charged nucleus
• contained protons
and electrons
scattered around the
outside
Early Atom Models:
What is the Bohr
Model?
• electrons (-) move in
definite ___________
around the nucleus
• Nucleus is made of
______________ (+)
and
________________
(neutral).
Modern Atom
Model: What is the
The Electron
Cloud Model?
• sometimes called the
wave model
• spherical cloud of
varying density
• varying density shows
where an electron is
more or less likely to
be
• The Bohr Model is still
used to help explain
characteristics of the
atom.
• ______________ charged
particles (+)
What are
Protons? ++ +
+ + +
+ +
-
-
-
+
-
-
• help make up the
___________ of the atom
• equal to the
_________________ of
the atom
• contribute to the
_______________
• equal to the ___________
of ________________ in a
neutral atom.
What are
Neutrons?
-
++ +
+ + +
+ +
-
-
-
• ____________
particles; have
no electric
charge
• help make up
the nucleus of
the atom
• contribute to
the _________
__________.
What are
Electrons?
-
-
-
• found _____________ the
nucleus of the atom in the
electron _____________.
++ +
+ + +
+ +
-
-
• ______________ charged
particles (-)
-
• each orbital/level can hold
a maximum number of
electrons
• 1st orbital = _________
• 2nd orbital = _________
• 3rd orbital = _________
What are
Electrons?
-
++ +
+ + +
+ +
-
-
-
• move so rapidly around
the nucleus that they
create an
_____________________
-
• mass is insignificant when
compared to protons and
neutrons
• equal to the _________ of
_____________________
in a neutral atom
• involved in the formation of
chemical bonds
What are Valence • found in the outermost
energy level of the
Electrons?
electron cloud (called
the ______________)
• involved in bonding
• determine the chemical
properties of an element
How is the Atom’s Center Formed?
Protons and neutrons are grouped together to form
the “center” or ________________ of an atom
Notice that the electrons are not a part of the nucleus
-
-
+
-
+ +
-
Atomic Structure
How are
Atoms
Described?
The Atomic
Symbol:
• atomic number =
________________
• in a _____________
atom, the # of protons
= the # of electrons
• atomic mass=
_________________ +
_________________
• the number of
protons in the
nucleus of an
atom
What is Atomic
Number?
-
-
+
++
-
What would be the atomic
number of this atom?
What is the Atomic
Mass?
•
the total number of protons
and neutrons in an atom’s
nucleus
•
expressed in Atomic Mass
Units (amu)
– each proton or neutron
has a mass of 1 amu
What would be the atomic
mass of this atom?
+
-
3
+
++
 4
3 protons + 4 neutrons =
an atomic mass of 7 amu
Why did we not account for the
electrons when calculating the
mass number?
-
-
Hydrogen (H) Atom
• Let’s use the Bohr Model to sketch a hydrogen
atom.
• notice the one electron in the first orbital
P = Atomic # =
E=P=
N = Atomic Mass – Atomic # =
Oxygen (O) Atom
• notice the two electrons in the first orbital/level and
the six in the second
Bohr Diagram
P = Atomic #
________
E=P
________
N = Atomic
Mass – Atomic #
________
Sodium (Na) Atom
• notice the two electrons in the first orbital/level, eight in
the second, and one in the third
Bohr Diagram
P=
E=
N=