Download Power Point Atomic Theory 2016

Atomic Structure
Democritus 460 BC
► Greek
Philosopher
► Suggested world was made of
two things – empty space and
“atomos”
 Atomos – Greek word for
uncuttable
►2
Main ideas
 Atoms are the smallest possible
particle of matter
 There are different types of
atoms for each material
2
John Dalton’s Atomic Theory
1804
1. All matter is made of atoms.
2. Atoms of one element are all
the same.
3. Atoms cannot be broken down
into smaller parts
4. Compounds form by
combining atoms
Dalton’s Early Atomic Model
► “Billiard
Ball” model
–viewed atoms as
tiny, solid balls
J.J. Thomson
1897
Discovered the electron
He was the first scientist to show the
atom was made of even smaller things
JJ Thomson
► Used
the Cathode ray tube to discover
electrons
Thomson’s Experiment
Voltage source
-
+
Vacuum tube
Metal Disks
Thomson’s Experiment
Voltage source
-
+
Thomson’s Experiment
Voltage source
-
+
Thomson’s Experiment
Voltage source
 Passing
+
an electric current makes a
beam appear to move from the
negative to the positive end
Thomson’s Experiment
Voltage source
 Passing
+
an electric current makes a
beam appear to move from the
negative to the positive end
Thomson’s Experiment
Voltage source
 Passing
+
an electric current makes a
beam appear to move from the
negative to the positive end
Thomson’s Experiment
Voltage source
 Passing
+
an electric current makes a
beam appear to move from the
negative to the positive end
Thomson’s Experiment
Voltage source
►By
adding an electric field
Thomson’s Experiment
Voltage source
+
 By
adding an electric field
Thomson’s Experiment
Voltage source
+
 By
adding an electric field
Thomson’s Experiment
Voltage source
+
 By
adding an electric field
Thomson’s Experiment
Voltage source
+
 By
adding an electric field
Thomson’s Experiment
Voltage source
+
 By
adding an electric field
Thomson’s Experiment
Voltage source
+
 By
adding an electric field he found
that the moving pieces were negative
Thomson’s “Plum Pudding” Model
Democritus, Dalton, Thomson Video
Ernest Rutherford
*1912-1913
Discovered
protons and
the nucleus
Ernest Rutherford
► He
showed that atoms
have (+) particles in the
center and are mostly
empty space
► He called the (+)
particles protons
► He called the center of
the atom the nucleus
Rutherford’s Scattering Apparatus
Alpha particles (+) bounce off of
the positively-charged nucleus, but
they go straight through the
electron cloud.
Rutherford’s Contribution
►The
atom is
mostly empty
space.
►The nucleus is
a small, dense
core with a
positive charge.
Gold Foil video
Rutherford’s Atomic Model
Structure of the Atom
► Atom
– smallest particle of an element that can
exist alone
 Two regions of an atom
►Nucleus
 Center of atom
 Protons and neutrons
►Electron
“cloud”
 Area surrounding nucleus
containing electrons
Structure of the Atom
► Proton
– Positive charge (+), 1 atomic
mass unit (amu); found in the nucleus
 amu -Approximate mass of a proton or a
neutron
► Neutron
– Neutral charge (0), 1 amu;
found in the nucleus
► Electron – Negative charge (-), mass is
VERY small
Counting Atoms
► Atomic
Number
 Number of protons in nucleus
 The number of protons determines identity
of the element!!
► Mass
Number (Atomic Mass)
 Number of protons + neutrons
 Units are g/mol
Counting Atoms
► Isotopes
 Atoms of the same element with varying
number of neutrons
 Different isotopes have different mass numbers
because the number of neutrons is different
Composition of the atom video
Start at 3:25
Counting Atoms
 Nuclear Symbol Notation
Atoms
► Protons
have a positive (+) charge and
electrons have a negative (-) charge
► In
a neutral atom, the number of protons
equals the number of electrons, so the
overall charge is zero (0)
 Example/ Helium, with an atomic number of 2,
has 2 protons and 2 electrons when stable
Ions
► In
a neutral atom
 Atomic number = # of protons = #of electrons
► Sometimes
atoms will gain or lose electrons
and form IONS
► Because an electron has a negative charge:
 When an atom GAINS electrons it becomes
NEGATIVE
 When an atom LOSES electrons it becomes
POSITIVE
Ions
Cation = a positive ion
Anion = a negative ion
Let’s Practice
► Aluminum





(Al) (no periodic table)
Protons = 13
Electrons =
Neutrons = 14
Atomic Number =
Atomic Mass =
Let’s Practice w/ nuclear symbol
notation
► Nuclear
Symbol notation
(no periodic table)





Protons =
Electrons =
Neutrons =
Atomic Number =
Atomic Mass =
Ag
108
47
Let’s Practice w/ isotopes
► use





the periodic table
Protons =
Electrons =
Neutrons =
Atomic Number =
Atomic Mass =
Uranium-235
Let’s Practice with Ions
Use the periodic table
 Charge =
 Protons =
 Electrons =
 Neutrons =
 Atomic Number =
 Atomic Mass =
39
K
1+