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Atom Notes
 Chemistry – the science that
studies the properties of
substances and how they react
with each other.
Review Notes
 Matter is made of particles called
atoms that are too small to see
with the eyes.
 Matter can not created or
destroyed.
 Matter can be an element, a
compound, or a mixture.
Review Notes
 Elements are the simplest
substances.
 Matter can undergo physical and
chemical changes.
How small are atoms?
There are 2 x 1022 zinc and copper
atoms in an ordinary penny!
That is
20,000,000,000,000,000,000,000!
Types of Atoms in
Earth’s Crust
 Hydrogen makes up about 90%
of the total mass of the universe.
 In Earth’s crust,
 47%
 28%
 12%
 8%
 5%
Oxygen
Silicon
Other elements
Aluminum
Iron
Types of Atoms in
Living Things
 Living things are mostly oxygen,
carbon, hydrogen, and nitrogen,
plus more than 20 other
elements.
 In humans,
 61%
 23%
 10%
 3%
 3%
Oxygen
Carbon
Hydrogen
Nitrogen
Other elements
Names and Symbols of
Elements
 Elements get their names in
different ways.
 Elements can be named from
people, places, and Greek words.
 Each element has a unique
symbol.
Elements have unique atoms
 Every atom of a specific element,
such as silver, is similar to every
other atom of the same element.
 Every atom of a specific element
is different from an atom of a
different element.
 How? It’s all about the structure
of the atom!
What is inside an atom?
 Nucleus – the dense center of
the atom made of protons and
neutrons
p
Protons
Neutrons
Nucleus
p
p
p
p
p
Let’s be positive!
 Protons – positively charged
particles in the nucleus: p+
p
Protons
Neutrons
Nucleus
p
p
p
p
p
Protons have a mass of one amu
I don’t get a charge out of you
 Neutrons - neutral particles in
the nucleus: n0
p
Protons
Neutrons
Nucleus
p
p
p
p
p
Neutrons have a mass of one amu
What is on the outside?
 Electrons – Negatively charged
particles that orbit the nucleus
in energy levels: ep
Protons
Neutrons
Electrons
Shell
Nucleus
p
p
p
p
p
Neutral atoms have balance!
 In neutral atoms the # of protons
equals the # of electrons, but the
neutrons can be different
5
4
5
p
Protons
Neutrons
Electrons
Shell
Nucleus
p
p
p
p
p
Forces in the Atom, part 1
Gravity: pulls objects
toward one another. It
depends on the mass of
the object and how
far apart the
objects are
The force of gravity
in atoms is very
small.
Forces in the Atom, part 2
Electromagnetic
Force: protons
and electrons
are attracted to
each other
because they
have opposite
charges
Forces in the Atom, part 3
Strong Force: protons
repel each other
because they have
the same charge.
The strong force
overcomes this
repulsion to hold the
nucleus together.
Forces in the Atom, part 4
The Weak Force: is
an important force
in radioactive
atoms.