Download Atoms and elements

WHAT IS AN ATOM?
Try to come up with your own definition. Now turn to your partner and
discuss.
SCIENTISTS WHO HELPED DEVELOP
THE ATOM! WHAT DID THEY DO?
•Dalton
•J.J. Thomson
•Rutherford
•Bohr
• * In the early 1800s, John Dalton
DALTON
performed experiments with gases.
• His results convinced him that
matter was made up of tiny
particles.
• …and that each element must be
made of its own unique kind of
particle and that these particles
combine in simple ways.
DALTON
• Dalton called these basic particles atoms
and pictured them as tiny, spheres.
DALTON’S MODEL
1.All matter is composed of tiny, indivisible
particles called atoms.
2.Atoms of each element are exactly alike.
3.Atoms of different elements have different
masses.
4.Atoms of different elements can join to
form compounds.
J.J. THOMSON
• At the end of the 1800s, J. J.
Thomson discovered that atoms
were not just simple, solid spheres
and contained even smaller,
subatomic particles.
• The subatomic particles Thomson
discovered were very small and
negatively charged.
• Thompson called them electrons.
THOMSON’S MODEL
• Thomson knew that atoms are
electrically neutral. Therefore, he
reasoned, an atom must contain
enough positive charge to balance
the negative charge of the
electrons.
• Thomson developed an atomic model
in which electrons were stuck into a
positively charged sphere.
“Plum Pudding Model”
• A positive charge in the substance of
the sphere balanced the electrons'
charge .
RUTHERFORD
His Model:
His Experiment:
After experimenting
with a beam of
positively charged
light, he concluded
that the protons are
concentrated in a
small area at the
center of the atom.
He called this region
the nucleus.
MOST OF ATOM IS
EMPTY SPACE!!
In his model, an atom
is mostly empty
space. The nucleus is
tiny compared to the
whole atom, but it
contains nearly all the
atom's mass.
http://www.mhhe.com/physsci/chemistry/ess
entialchemistry/flash/ruther14.swf
BOHR’S MODEL
• He proposed that each electron in
an atom has a fixed amount of
energy.
• This energy keeps an electron
moving around the nucleus within a
specific region called an energy
level.
• In Bohr's model, energy levels
surround the nucleus in rings or
shells, like the layers of an onion.
ELECTRON CLOUD MODEL
• Today scientists know that electrons do not actually orbit the
nucleus as in Bohr's planetary model.
• The electron cloud model is now used to describe atoms.
• In this model, electrons dart about within an energy level in an
ever-changing path.
• Most of this path falls into a region called an electron cloud.
• At any given time, there is a high probability that the
electron exists in the electron cloud.
ATOMS AND ELEMENTS
• Atoms are the building blocks of the universe.
• Scientists have identified nearly 100 different kinds
of naturally occurring atoms.
• Each kind of atom has unique properties and is called
an element.
• An atom of an element can't be broken down and
retain its properties.
PARTICLES INSIDE AN ATOM
• Inside the Nucleus: Center of the atom
• Neutrons- neutral charged particles
• Protons- positive charged particles
• Outside the Nucleus:
• Electrons- negatively charged particles
CHECK FOR UNDERSTANDING
• Fill in the chart about the 3 particles of the atom!
Particle
Proton
Electron
Neutron
Charge
Location
TAKE A CLOSER LOOK…
• Atomic number: 11
• Sodium contains 11 protons and 11
electrons!
• Atomic mass: 22.990
• Mass number: 23 (rounded number)
• Number of Neutrons in Sodium:
• Mass number (23)-atomic number
(11)= 12 neutrons
OCTOBER 14TH
#
__
• What is an atom?
• What are the 3 particles found in an atom? What are their
charges?
• TAKE OUT YOUR PERIODIC TABLES AND IDENTIFY THE ATOMIC NUMBER
AND ATOMIC MASS FOR EACH ELEMENT. HOW MANY PROTONS
NEUTRONS AND ELECTRONS ARE IN EACH ELEMENT?
1. POTASSIUM
2. PHOSPHORUS
OCTOBER 15TH
• Take out your periodic table of elements.
• Find KRYPTON (Kr)
• How many protons:
• How many electrons:
• How many neutrons: (new number):
# __