Transcript Atoms - IES Al

Daltons Atomic Theory
• Dalton stated that
elements consisted of
tiny particles called atoms
• He also called the
elements pure
substances because all
atoms of an element
were identical and that in
particular they had the
same mass.
Dalton’s Atomic Theory
1. All matter consists of tiny particles.
Dalton, like the Greeks, called these particles “atoms”.
2. Atoms of one element can neither be subdivided nor changed into
atoms of any other element.
3. Atoms can neither be created nor destroyed.
4. All atoms of the same element are identical in mass, size, and
other properties.
5. Atoms of one element differ in mass and other properties from
atoms of other elements.
6. In compounds, atoms of different elements combine in simple, whole
number ratios.
Thomson Model of the Atom
• J.J. Thomson discovered the electron and knew that
electrons could be emitted from matter (1897).
• William Thomson proposed that atoms consist of small,
negative electrons embedded in a massive, positive
sphere.
• The electrons were like currants in a plum pudding.
• This is called the ‘plum pudding’ model of the atom.
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electrons
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-
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J.J. Thomson
• He proved that atoms of
any element can be
made to emit tiny
negative particles.
• From this he concluded
that ALL atoms must
contain these negative
particles.
• He knew that atoms did
not have a net negative
charge and so there must
be balancing the negative
charge.
J.J. Thomson
William Thomson
(Lord Kelvin)
• In 1910 proposed
the Plum Pudding
model
– Negative electrons
were embedded into
a positively charged
spherical cloud.
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 56
Spherical cloud of
Positive charge
Electrons
http:
• http://rabfis15.uco.es/Modelos%20At%c3
%b3micos%20.NET/Modelos/Experiencias
/ExperienciaRutherford.aspx
Rutherford Experiment.
Structure of the Atom 3: The
Rutherford Model
• http://www.youtube.com/watch?v=FfY4R5
mkMY8
• http://www.authorstream.com/Presentation
/cchschem-33220-atomic-structureentertainment-ppt-powerpoint/
Particles in the Atom
Electrons
(-) charge
no mass
located outside the nucleus
1 amu
located inside the nucleus
1 amu
located inside the nucleus
Protons
(+) charge
Neutrons
no charge
Discovery of the Neutron
9
4
Be
+
4
2
He
12
6
C
+
1
0
n
James Chadwick bombarded beryllium-9 with alpha particles,
carbon-12 atoms were formed, and neutrons were emitted.
Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 764
*Walter Boethe
Subatomic particles
Name
Symbol
Relative
Charge mass
Actual
mass (g)
Electron
e-
-1
1/1840
9.11 x 10-28
Proton
p+
+1
1
1.67 x 10-24
Neutron
no
0
1
1.67 x 10-24
Subatomic Particles
ATOM
ATOM
NUCLEUS
NUCLEUS
ELECTRONS
ELECTRONS
PROTONS
PROTONS
NEUTRONS
NEUTRONS
POSITIVE
Positive
CHARGE
Charge
NEUTRAL
Neutral
CHARGE
Charge
NEGATIVE
CHARGE
Negative Charge
equal in a
Atomic
Most Number
of the atom’s mass.
neutral atom
equals the # of...
QUARKS
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem