Transcript The Development of Atomic Theory

The Development of
Atomic Theory
10.1 The Nature of
Matter
Matter is a term used to describe anything
that has mass and takes up space.
Greek philosophers Democritus and
Leucippus proposed that matter is made
of tiny particles called atoms.
Atoms were an idea that few believed.
The first evidence was called Brownian
motion for Robert Brown, who first noticed
the jerky motion of tiny particles.(1827)
Democritus
Atom from the Greek word
atomos that means indivisible
Democritus
Proposed that all atoms are small hard
particles made of a single material
Different shapes and sizes
Atoms are always moving
They form different materials by joining
together
John Dalton(1803)
All substances are made of atoms.
Atoms are small particles that cannot be
created, divided, or destroyed.
Atoms of the same element are exactly
alike (1803)
The solid sphere model - like a sour ball
An early model
In 1897 English physicist J. J.
Thomson discovered that
electricity passing through a
gas caused the gas to give off
particles that were too small to
be atoms.
These negative particles were
eventually called “electrons.”
Plum –Pudding ModelChocolate Chip Cookie
Model
The atom is mostly positively charged
material.
Electrons are small, negatively charged
particles located throughout the positive
material.
Proved atoms can be divided into
smaller parts
Ernest Rutherford
Designed an experiment to test
Thomson’s theory.
Proposed that in the center of the atom
is a tiny dense positively charged region
called the nucleus.
Tootsie roll pop
Rutherford’s Gold Foil
Experiment
He aimed a beam of small positively
charged particles at a sheet of gold
foil.The particles were larger than
protons.
The nuclear model
In 1911, Ernest
Rutherford, Hans
Geiger, and Ernest
Marsden did a clever
experiment to test
Thomson’s model.
We now know that every
atom has a tiny nucleus,
which contains more
than 99% of the atom’s
mass.
Bohr’s Model of the
Atom
Electrons travel in definite paths around
the nucleus. These paths are located in
levels at certain distances from the
nucleus
Gob stopper model
Bohr Model
A Planetary Model of the Atom
Erwin Schrodinger and
Werner Heisenberg
Ferrero Rocher Model
They explained the nature of
electrons in an atom
Electrons and the Periodic
Table
Order of filling
levels
Energy levels
These levels are divided into smaller
regions called orbitals.
These regions are designated by the
following letters
s,p,d and f
Orbitals
s- can hold 2 electrons
p- can hold 6 electrons
d- can hold 10 electrons
f- can hold 14 electrons
Orbitals
The Atomic Orbitals
Atom in a Box
Real-Time
Visualization of the
Quantum Mechanical
Atomic Orbitals
The orbital images on
this page represent the
shape of the atomic
orbitals. The clouds you
see are the probability
distribution of an
electron bound to a
Hydrogen nucleus.
The Modern Atomic
Theory
Electrons do not travel in definite paths
as Bohr had suggested
The exact path of a moving electron
cannot be predicted.
Electron clouds are regions inside the
atom where electrons are likely to be
found
10.1 Atoms
A single atom is the smallest particle that
retains the chemical identity of the element.
10.1 Molecules
A molecule is a group of two or more
atoms joined together chemically.