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Chapter 17 Sec 1-4
Structure of the Atom
Elements

Any material made up of only one type of
atom is classified as an element.
Example – Pure gold contains only gold
atoms
 Example – Nitrogen gas contains only
nitrogen atoms
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All the elements are listed on a chart
called the periodic table.
Scientific Shortcuts!
Do you have a nickname?
 What about abbreviations for the names of
states or classes?


EX: PS – Physical Science
IL – Illinois
Scientists do this too – especially in
CHEMISTRY!
Chemistry Shortcuts!




Elements are abbreviated
with certain atomic
symbols.
Many of these symbols
come from Latin roots.
Elements are named after
people, places, or
properties.
EX: H for Hydrogen
He for Helium
O for Oxygen
Fe for Iron
Hydrogen

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
Hydrogen was the
first element to exist
in the universe.
It is the most common
element – makes up
more than 90% of all
atoms.
Hydrogen is very light
and has a simple
structure.
Size of an Atom
Atoms are so small they can’t be seen with
visible light.
 We could stack microscope upon
microscope and never be able to “see” an
atom.
 Photographs of atoms are obtained with a
scanning tunneling microscope.


This is a non-light imaging device that
bypasses light and optics.
Atomic Components
Remember Your Charges!!

Protons and Neutrons
are found in the
nucleus of the atom


Nucleus is the positive
center of the atom
Electrons are circling
around the outside of
the nucleus.
Atomic Nucleus
The atomic nucleus contains protons and
neutrons.
 It makes up most of the mass of the atom,
even though it is extremely small.
 Electrons move around the nucleus.
 Most of the rest of the atom is empty
space.

Parts of the Atom
Subatomic Particle
Mass
Compared
to an
Electron
Particle
Charge
Symbol
Location
Proton
+1
p+
1836
Nucleus
Neutron
0
n0
1841
Nucleus
Electron
-1
e-
1
Electron
Cloud
Let’s get on with the Chemistry!
ATOMIC NUMBER=# of protons in
nucleus of atom
 Always whole numbers!
 Each atomic number is unique to a
particular element!
Ex: All atoms with the atomic number 8 are
oxygen atoms, all oxygen atoms have the
atomic number 8!

Mass Number
MASS NUMBER = total # of particles in
the nucleus
 MASS NUMBER = total number of protons
and neutrons
Ex: Boron has mass number of 11 and
atomic number of 5. So it has 5 protons
and 6 neutrons.

Isotopes
ISOTOPES=atoms of the same element
with different numbers of neutrons.
 A majority of elements exist as isotopes.
Ex: Helium

4 Neutrons
5 Neutrons
Isotope Symbols
Mass
Number
Atomic
Number
56
Fe
26
Atomic
Symbol
• The superscript is the atomic mass.
• The subscript is the atomic number.
Atomic Mass
The total mass of an atom is the atomic
mass.
 This is an average mass! It’s the average
mass of all its various isotopes!
 This is the mass shown on the periodic
table.
 Elements have different masses!

ATOMIC
NUMBER
ATOMIC
MASS
And they all lived happily ever
after in Chemistryland!