Transcript The Chemical Behavior of Atoms

The Chemical Behavior of
Atoms
Day 1
Curriculum
 Big Idea: Atomic theory is the foundation for the
study of chemistry.
 Concept: Energy is absorbed or emitted when
electrons move from one energy level to another
within the atom.
 PA Standard: “Recognize discoveries from Dalton
(atomic theory), Thomson (the electron), Rutherford
(the nucleus), and Bohr (planetary model of atom),
and understand how each discovery leads to modern
theory. Describe Rutherford’s “gold foil” experiment
that led to the discovery of the nuclear atom.”
Today’s Agenda 2/15/11
Opener: What is an electron?
Go over homework – in small groups and as a class.
Review of atomic theory as a class and Activity 4: Inquiring
Further
 Periodic Table: The Chemical Behavior of Atoms
 (Periodic Table Activity 5 – See handout)
1. What Do You Think?
2. For You To Do
3. Powerpoint on Electrons
 Closure Question
Take Home Assignment: Read Chem Talk (pages 104-106, and
answer the Checking Up Questions – p. 106
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Quiz Thursday on Elements and Their Symbols – See Handout
Atom:
the smallest particle of an
element that retains its identity
in a chemical reaction
Democritus
 Among the first to
suggest the
existence of atoms
 Believed that
matter consisted of
tiny, indivisible,
unchangeable
particles called
atoms
 His ideas did not
explain chemical
behavior and lacked
experimental
support
Dalton
 Used experimental
methods to
transform
Democritus’s ideas
on atoms into a
scientific theory.
Dalton’s Atomic Theory
1.
2.
3.
4.
All elements are compiled of tiny indivisible particles
called atoms.
Atoms of the same element are identical. The atoms
of any one element are different from those of any
other element.
Atoms of different elements can physically mix
together or can chemically combine in simple wholenumber ratios to form compounds.
Chemical reactions occur when atoms are separated,
joined, or rearranged. Atoms of one element,
however, are never changed into atoms of another
element as a result of a chemical reaction.
Cathode Ray Tube Experiment
 http://www.chem.uiuc.edu/clcwebsite
/cathode.html#
 Thompson found the charge to mass
ratio of the electron to be constant,
and concluded that electrons must be
parts of the atoms of all elements.
Subatomic Particles
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Electrons
Negatively charged with very small
mass
Located in orbitals, outside the
nucleus
Discovered by J.J. Thompson
Cathode Ray Tube Experiment
Protons and Neutrons… later
J. J. Thompson’s Plum Pudding
Model
Rutherford’s Gold Foil Experiment
Rutherford’s Gold Foil
Experiment
“This is almost as incredible as if you
fired a 15-inch shell at a piece of
tissue paper and it came back and hit
you.”
 The atom is mostly empty space.
 The atom has a small, dense core
where all of the positive charge is
located.
Atomic Number
 The whole numbers in the blocks of
the periodic table
 The number of protons in one atom of
a given element
 The number of electrons in a
NEUTRAL atom of a given element
 Every element has a different number
of protons.
Protons, Neutrons, Electrons
The Bohr Model
 Bohr proposed that an
electron is found only
in specific circular
paths, or orbits,
around the nucleus.
 Energy Levels: The
fixed energies an
electron can have
 Quantum: The amount
of energy required to
move an electron from
one energy level to
another
The Quantum Mechanical Model
 is based on
mathematical
equations
developed by Erwin
Schrodinger
 determines the allowed
energies an electron can
have and how likely it is
to find the electron in
various locations around
the nucleus.
Atomic Orbitals
 regions of space
in which there is
a high
probability of
finding an
electron
Closure Question
How is light emitted from an atom?