PROPERTIES OF THE ATOM & THE
PERIODIC TABLE
Section 1: Structure of the Atom
SCIENTIFIC SHORTHAND
• Elements on the periodic table are represented by
symbols.
• Chemical symbols consist of one capital letter or a
capital letter plus one or two lowercase letters.
• The symbol for silver is Ag. Silver’s Latin name is
Argentum.
• The symbol for gold is Au. Gold’s Latin name is
Aurum.
• Plumbium is lead’s Latin name. Lead’s symbol is
Pb.
• A subscript to the right of a symbol indicates the
number of atoms of that particular element present in a
compound.
ATOMIC COMPONENTS—
PARTS OF THE ATOM
• An atom is the smallest piece of matter that
still keeps the properties of the element.
• The element silver is only silver atoms,
uranium atoms are only uranium atoms.
• Atoms are different from one another
because of the number of PROTONS they
have.
• Silver always has 47 protons
• Uranium always has 92 protons.
THE PARTS . . .
• The nucleus is the center of the atom. It is
made up of:
• protons, with a positive electrical charge (+),
• neutrons with a neutral charge (no charge).
• The electrons are found outside the nucleus in
what is called a cloud.
• Electrons have a negative electrical charge
(-).
• Electrons are approximately 1/10,000 the
size of a proton or neutron.
EVEN SMALLER PARTS . . .
• Smaller particles make up protons and
neutrons.
• These are called quarks.
• There are six kinds of quarks - up quarks,
down quarks, strange quarks, charm quarks,
bottom quarks, and top quarks. Their names
don't really mean anything, just that they are
different kinds of quarks.
MORE ON QUARKS . . .
• Quarks were hard to find.
• Particles had to be accelerated into collisions
with great force and speed.
• The Tevatron at the Fermi Accelerator in
Illinois was used for these experiments.
• It is about 6.4 km in circumference and uses
electric and magentic fields to accelerate,
focus, and collide particles.
• Particles are detected using computers and
other particles.
MORE ON QUARKS . . .
• In order to understand their calculations,
physicists assigned the quarks fractional
electrical charges of 2/3 and -1/3.
• Such charges had never been observed
before.
• Quarks are never observed by themselves,
and so initially these quarks were regarded
as mathematical fiction.
• Experiments have since convinced
physicists that not only do quarks exist, but
there are six of them, not three.
EVEN SMALLER PARTS . . .
• The top quark was discovered last.
• It is the most massive quark.
• It had been predicted for a long time but had
never been observed successfully until 1995.
• A team of nearly 450 scientists helped to “find”
it.
FERMILAB . . .
Tevatron Collider was shut down September 30 ,
2011
BUBBLE CHAMBERS . . .
• Old bubble chamber at Fermi
• Used to capture images of the
tracks of subatomic partices
after collisions.
ACCELERATORS IN HISTORY
• http://en.wikipedia.org/wiki/List_of_accelerators_
in_particle_physics
NEW ACCELERATORS
• Large Hadron Collider:
• http://www.telegraph.co.uk/science/largehadron-collider/8675126/Spectacular-imagesfrom-Big-Bang-recreation.html
MORE
• A proton is made of two up quarks and a down
quark.
• A neutron is made of two down quarks and an
up quark.
• A force called the strong nuclear force holds the
quarks together.
• Up quarks have a little bit of mass, but most of
the mass of a proton comes from the strong
nuclear force itself, rather than from the quarks.
PARTICLES NAMES WE
AREN’T GOING TO TALK
ABOUT (MUCH) 
• Leptons, fermions, muons, neutrinos, hadrons,
bosons
• http://dsc.discovery.com/tvshows/curiosity/topics/subatomic-particles-in-anutshell.htm
JUST HOW SMALL IS AN ATOM?
• https://www.youtube.com/watch?v=yQP4U
JhNn0I&feature=player_embedded
• There are about 5 sextillion atoms in a
drop of water.
• That’s about
5,000,000,000,000,000,000,000 atoms of
hydrogen and oxygen.
USING MODELS TO UNDERSTAND
• Models allow you to see something that is
either too large or too small, or to envision
something that has not yet been built.
• Scaled-down models
– The globe
– The solar system
– Airplanes
– Buildings
USING MODELS TO UNDERSTAND
• Scaled-up models
– Bacteria
– Other cells
– Atoms and compounds
EARLY IDEAS OF ATOMS
• Democritus was a
Greek philosopher
who lived from 480
BC to 370 BC.
• He created a theory
that argued that
there are various
basic elements which
always existed but
can be rearranged
into many different
forms.
DEMOCRITUS—THE GREEK DUDE
• Democritus said that matter is
made up of small particles
• Named the parts of matter
atomos, which means
“uncuttable.”
• Quote: “By convention there
is sweet, by convention there
is bitterness, by convention
hot and cold, by convention
color; but in reality there are
only atoms and the void.”
ARISTOTLE ARGUED
• Another Greek philosopher
named Aristotle argued that
matter was the same
throughout and NOT composed
of small particles.
• He believed that every thing
was made of its own type of
matter, so, in essence, a table
was made of table matter.
• This idea actually stuck for
almost 2,000 years—over
Democritus’s idea.
JOHN DALTON
• Lived 6 September 1766 – 27 July 1844
• Was a schoolteacher and scientist in England
• Looked at Democritus’s ideas and also thought
atoms were tiny solid masses that make up
matter.
• Dalton first published his theories on atoms in
1808 in a small book titled A New System of
Chemical Philosophy. The book had an
enormous influence on the development of
both chemistry and physics.
JOHN DALTON’S ATOMIC THEORY
1. Elements are made of tiny
particles called atoms.
2. All atoms of a given element
are identical.
3. The atoms of a given element
are different from those of any
other element.
4. Atoms of one element can combine with atoms
of other elements to form chemical
compounds; a given compound always has the
same relative numbers of types of atoms.
5. Atoms cannot be created, divided into smaller
particles, nor destroyed in the chemical
process; a chemical reaction simply changes
the way atoms are grouped together.
•
•
•
•
J.J. THOMSON’S DISCOVERY OF THE
NEGATIVE CHARGE (ELECTRON) IN 1897
Click here for Thomson's
discovery
He took Dalton’s “spherical
atoms” idea and found that
there is a negative charge
associated with the particles.
He imagined the negative
particles to be like the raisins
embedded in a plum pudding.
I like to compare it to a blob of
chocolate chip cookie dough.
BOHR’S MODEL
• Danish physicist Niels Bohr, 1913
• Hypothesized that electrons travel in fixed
orbis around the atom’s nucleus
• In 1911 Ernest Rutherford and his student
James Chadwick discovered that the nucleus
contained positive protons and neutral
neutrons.
• We use this model today to understand the
basic structure of the atom
• Rutherford's experiment to detect the nucleus
ELECTRON CLOUD MODEL 1926
• An electron cloud is the area around the
nucleus of an atom where its electrons are
most likely found.
• The cloud’s diameter is 100,000 times larger
than the diameter of the nucleus.
• Therefore, most of an atom is made up of
empty space.
• It is not a good model to use to understand
electron placement and transfers, however.
ELECTRON CLOUD MODEL 1926
ORBITALS OF ATOMS
• The Electron Cloud Model is alternately called
the Atomic Orbital Model.
• Electrons actually travel more in “orbitals.”
• Orbitals give a more accurate placement of
electrons.
• Some periodic tables
state the electron
orbitals. They are
shown at the right.
ORBITALS OF ATOMS