Download atoms

The Atom
What is
Matter?
• anything that has
mass and takes up
space
• matter is made up
of atoms
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
Results
• 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 divided
• building blocks of all
matter
• comprised of a nucleus (at
it’s center) and an electron
cloud (surrounding the
nucleus)
What are Subatomic
Particles?
• made up of sub-atomic
particles
• smaller than an atom
• protons
• neutrons
• electrons
Early Atom Models:
What is the
Rutherford Model?
• mostly empty space
• small, positive
nucleus
• contained protons
and electrons
scattered around the
outside
Early Atom Models:
What is the Bohr
Model?
• electrons move in
definite orbits
around the nucleus
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
What are
Protons?
• positively charged
particles (+)
++ +
+ + +
+ +
-
-
-
+
-
-
• help make up the
nucleus of the atom
• equal to the atomic
number of the
atom
• contribute to the
atomic mass
• equal to the
number of
electrons
What are
Neutrons?
-
++ +
+ + +
+ +
-
-
-
• neutral
particles;
have no
electric
charge
• help make up
the nucleus of
the atom
• contribute to
the atomic
mass
What are
Electrons?
• negatively charged
particles (-)
++ +
+ + +
+ +
-
-
-
-
• found outside the
nucleus of the atom in
the electron
orbits/levels
• each orbit/level can
hold a maximum
number of electrons
• 1st orbital = 2 electrons
• 2nd orbital = 8 electrons
• 3rd orbital = 8 electrons
What are
Electrons?
-
-
-
++ +
+ + +
+ +
-
-
• move so rapidly
around the nucleus
that they create an
electron cloud
-
-
• mass is insignificant
when compared to
protons and neutrons
• equal to the number
of protons
• involved in the
formation of chemical
bonds
What are Valence
Electrons?
• found in the
outermost energy
level of the electron
cloud (called the
valence shell)
• 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 nucleus of an atom
Notice that the electrons are not apart of the nucleus
-
-
+
-
+ +
-
Atomic Structure
How are Atoms
Described?
• atomic number =
number of protons
• in a neutral atom, the
# of protons = the #
of electrons
• atomic mass= the
number of protons +
the number of
neutrons
• 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
+ =1
=0
+
P = Atomic # =
E=P=
N = Atomic Mass – Atomic # =
=1
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=
Building Atoms
Using the whiteboard and the proton, neutron,
and electron pieces, build the following atoms,
and determine their atomic and mass numbers.
Atoms
Carbon
Beryllium
Oxygen
Lithium
Sodium
Protons
6
4
8
3
11
Neutrons
6
5
8
4
12
Electrons
6
4
8
3
11