Download Document

The Atom
I- Theories About the Atom:
A- The term Atom comes from
the Greek word meaning
“invisible” or “that which
cannot be further cut”. This
comes for the Greek thinker
Democritus more than 2000
year ago.
1-The Greeks believed that all
matter was made up four basic
elements
Fire
Air
Earth
Water
B-Dalton’s Model: in the early
1800’ John Dalton said the
atom was a solid particle that
could not be divided, and
each element had its own
kind of atom.
C-Thomson’s Model: in 1897
J.J. Thomson discovered that
the atom was made up of
smaller particle. Thomson
discovered the electron.
1- The atom was known to be
neutral. The atom must also
have a positive charged
particle.
a- Thomson never discovered the
positive particle but he knew it
existed.
b- His model known as
“Plum Pudding”
D-Rutherford’s Model: In
1908, Ernest Rutherford fired
a stream of tiny positively
charged particle at a very thin
sheet of gold foil. He
discovered the Nucleus of the
atom and found that it
contained what Thomson was
looking for the positively
charged particle the Proton.
1-Ruther Model is known as
“The Solar system”.
E-Bohr Model: In 1913 Niel
Bohr said that the electrons
move in a definite orbit
around the nucleus known
as.
1-Energy Level: is the path an
electron takes around the
nucleus of the atom, it related
to the amount of energy it has.
2-Electrons Energies: By heating
up or passing electricity
through the atom you can
increase its energy.
a-If the atom gains enough energy
the electron can jump to a
higher energy level called an
Excited State.
b- To return to it’s original state
the atom releases the extra
energy in the form of a PHOTON.
c-Spectrum is the finger print of an
element each element has its own
spectrum.
F-Chadwick’s Model: In 1932
Chadwick discovered a
particle in the nucleus of the
atom. The Neutron has NO
CHARGE but has more mass
than the proton. This
completed the model of the
atom.
Electron
Neutron
Proton
1-Today: the atom is described
as a central mass surrounded
by an electron cloud.
II- How Atoms Differ
A- All atoms of an element
have the same number of
protons. The number of
protons determines what
the element is.
1- Atomic Number is the
number of protons of an
atom.
2- Mass Number: is the total
number of Protons and
Neutrons in an atom.
a- To find the number of neutrons
in an atom all you do is
subtract the atomic number
from the mass number.
Mass Number
B-Isotopes: Atoms of the same
element with the same atomic
number but a different number
of neutrons.
III-Classifying Elements:
A-The Periodic Table: Was
created by Mendeleev, he
put the elements with the
same characteristics into
columns.
1-The elements line up in
increasing atomic
numbers.
B- Arrangement of Table:
1-Each row is called a
period and each column
is called a group.
2-If you know something
about an element in a
group you know
something about them
all.
3-Each box has an
element’s symbol, name,
atomic number, mass
number, and the number
of electrons in each
energy level.
Atomic Number
Symbol
Name
13
2
Al
8
3
Aluminum
26.98
Number
of
electrons
in each
energy
level
Average atomic mass