What is Matter?
• http://learn.genetics.utah.edu/content/begi
n/cells/scale/
What is Matter?
• Any thing that occupies space (volume) and
has mass
• Can be visible or invisible to the naked eye
• All matter is composed of atoms
Atomic Size

At sea level, one cubic
centimeter of air (size of
a sugar cube, or marble)
will have 45 billion billion
atoms within it.


45,000,000,000,000,000,000
How many atoms would it
take to fill a universe?
Count to 45,000,000,000,000,000,000

Fill Lincoln high school
COMPLETELY with marbles.

Empty and re-fill it once a
MINUTE (24 hours per day).

After 400,000 years, you would
have
45,000,000,000,000,000,000.
Atoms
1. All substances are made from atoms.
2. There are about 100 different types of
atoms
3. An element is a substance which
contains only one type of atom
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S.MORRIS 2006
HISTORY OF THE ATOM
460 BC
Democritus develops the idea of atoms
he pounded up materials in his pestle and
mortar until he had reduced them to smaller
and smaller particles which he called
ATOMA
(greek for indivisible)
HISTORY OF THE ATOM
1808
John Dalton
suggested that all matter was made up of
tiny spheres that were able to bounce around
with perfect elasticity and called them
ATOMS
HISTORY OF THE ATOM
1898
Joseph John Thompson
found that atoms could sometimes eject a far
smaller negative particle which he called an
ELECTRON
HISTORY OF THE ATOM
1904
Thompson develops the idea that an atom was made up of
electrons scattered unevenly within an elastic sphere surrounded
by a soup of positive charge to balance the electron's charge
like plums surrounded by pudding.
PLUM PUDDING
MODEL
HISTORY OF THE ATOM
1910
Ernest Rutherford
oversaw Geiger and Marsden carrying out his
famous experiment.
They fired Helium nuclei at a piece of gold
foil which was only a few atoms thick.
They found that although most of them
passed through. About 1 in 10,000 hit
HISTORY OF THE ATOM
helium nuclei
gold foil
helium nuclei
They found that while most of the helium nuclei passed
through the foil, a small number were deflected and, to their
surprise, some helium nuclei bounced straight back.
HISTORY OF THE ATOM
Rutherford’s new evidence allowed him to propose a more
detailed model with a central nucleus.
He suggested that the positive charge was all in a central
nucleus. With this holding the electrons in place by electrical
attraction
However, this was not the end of the story.
HISTORY OF THE ATOM
1913
Niels Bohr
studied under Rutherford at the Victoria
University in Manchester.
Bohr refined Rutherford's idea by adding
that the electrons were in orbits. Rather
like planets orbiting the sun. With each
orbit only able to contain a set number of
electrons.
Bohr’s Atom
electrons in orbits
nucleus
HELIUM ATOM (atomic structure)
Shell
proton
+
-
N
N
+
electron
What do these particles consist of?
-
neutron
ATOMIC STRUCTURE
Particle
Charge
Mass
proton
1
neutron
-ve charge
1/
1000
ATOMIC STRUCTURE
Mass number
the number of protons and
neutrons in an atom
Atomic number
the number of protons in an atom
4
2
He
number of electrons = number of protons
Number of neutrons = mass nnumber – atomic number
ATOMIC STRUCTURE
Electrons are arranged in Energy Levels or
Shells around the nucleus of an atom.
•
first shell
a maximum of 2 electrons
•
second shell
a maximum of 8 electrons
•
third shell
a maximum of 8 electrons
ATOMIC STRUCTURE
There are two ways to represent the atomic
structure of an element or compound;
1.
Electronic Configuration
2.
Atom Diagrams
ELECTRONIC CONFIGURATION
With electronic configuration elements are represented
numerically by the number of electrons in their shells
and number of shells. For example;
Nitrogen
2 in 1st shell
5 in
2nd
shell
Has
2
+
7 protons so 7 electrons
5 = 7
Electron configuration = 2 , 5
14
7
N
ELECTRONIC CONFIGURATION
Write the electronic configuration for the following
elements;
a)
40
20
Ca
23
b)
2,8,8,2
d)
35
17
Cl
2,8,7
Na
11
c)
2,8,1
e)
28
14
Si
2,8,4
16
O
8
2,6
f)
11
5
B
2,3
DOT & CROSS DIAGRAMS
With Dot & Cross diagrams elements and compounds
are represented by Dots or Crosses to show electrons,
and circles to show the shells. For example;
X
Nitrogen
X X
N
X X
14
7
XX
N
DOT & CROSS DIAGRAMS
Draw the Dot & Cross diagrams for the following
elements;
XX
35
a)
X
16
8
O
b)
Cl
17
XX
X
Cl X
X
X
X
X
X
X
X
X
O X
X
X
X
X
X
X
X
X X
SUMMARY
1. The Atomic Number of an atom = number of
protons in the nucleus.
2. The Atomic Mass of an atom = number of
Protons + Neutrons in the nucleus.
3.
The number of Protons = Number of Electrons.
4.
Electrons orbit the nucleus in shells.
5.
Each shell can only carry a set number of electrons.
Isotopes
1. Isotopes are atoms of the same
element that have different numbers of
neutrons (e.g. carbon-12 and carbon14)
2. Isotopes have the same atomic
number but different mass numbers
Isotopes
What is an Ion?
• An ion is a charged
atom (or particle) and
can be either
positively or
negatively charged.
• Atoms can become
ions by either gaining
or loosing electrons
from their outer shell.
• These electrons in the
outer shell are called
Valence Electrons.
• The charge and
number depends on
how many valence
electrons are gained
or lost.
Where do these gained electrons come from?
How do metals loose electrons?
• These electrons are
gained from metals trying
to loose their valence
electrons trying to
become ions.
• Therefore, for elements to
become ions there must
be other elements
present to either accept
or give away electrons.
• If two ions join together
we can form c_______.