Atomic Structure. Matter Everything is made of matter. Matter has mass and occupies volume Matter is...
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Atomic Structure. Matter Everything is made of matter. Matter has mass and occupies volume Matter is made of atoms Atoms are the smallest unit of an element,
Matter Everything is made of matter. Matter has mass and
occupies volume Matter is made of atoms Atoms are the smallest unit
of an element, which is a type of matter.
Slide 3
What is an atom? An atom is the building block of all matter.
It is the smallest unit of a substance It has taken many years to
get to our current idea of the atom. Since atoms cant be seen,
scientists create models. A model is a representation of something
else.
Slide 4
The History of the Atomic Model The first atomic model was
created in 400 B.C. and was created by Democritus. He stated that
atoms were the smallest parts of substances, were indivisible and
indestructible, and called them atmos meaning not to be cut.
Democratus had no proof, only belief His theory was disputed by
Aristotle whose theory that matter was uniform throughout was
accepted for the next 2,000 years.
Slide 5
Mental Activity Atoms Exist
Slide 6
Out of the Dark Ages Daltons Model In 1803, John Dalton created
a model of the atom which was also a solid sphere. There were four
parts to Daltons Theory Each element was composed of identical
atoms. Atoms of different elements can physically or chemically
combine in simple whole number compounds. Atoms of one element can
never be changed into another. Chemical reactions occur when atoms
are separated, joined, or rearranged
Slide 7
Thompsons Plum Pudding Model J.J. Thompson was the first to
suggest that atoms are made of smaller particles. He passed an
electric current through a gas and noticed it gave off negatively
charged particles. Thompson concluded that the negatively charged
particles came from within the atom. Since the gas was not charged
there must also be a positively charged part of the atom. Thompson
had discovered the electron.
Slide 8
Thompsons Plum Pudding Model From his discovery of the
electron, Thompson created this model of the atom Atoms are
composed of negatively charged particles called electrons in a
positively charged pudding material.
Slide 9
Rutherfords Gold Foil Experiment
Slide 10
Rutherford's Gold Foil Experiment In this experiment, a narrow
stream of positively charged alpha particles were aimed at a piece
of gold foil. An alpha particle is a helium atom without electrons.
Most of the particles passed through the foil with no deflection,
while some bounced back. Why would this be a surprise?
Slide 11
Rutherford's Atomic Model The theory was that the positively
charged particles would pass through and be deflected by the like
charge of the positive pudding. Since this did not happen,
Rutherford theorized that most of the atom was empty space with
most of the mass and the positive charge at the center, called the
nucleus. Rutherford later discovered and named the positively
charged particle in the nucleus the proton.
Slide 12
The Rutherford Atomic Model The Rutherford Atomic Model had the
positive charge located in the center of the atom in a place called
the nucleus. The electrons were distributed in the empty space of
the atom.
Slide 13
Bohrs Planetary Model Rutherfords atomic model could not
explain the chemical properties of elements. In an attempt to
explain this, Niels Bohr theorized that the electrons orbited the
nucleus in specific circular paths. Each electron moves around the
nucleus with fixed energy called an energy level. To move to a
higher energy level, an electron must absorb a specific amount of
energy called a quantum
Slide 14
Bohrs Planetary Model Once an electron gains or loses the
quantum of energy it may move to a new orbit or energy level. This
model was accurate for hydrogen, but did not explain some of the
behaviors seen in atoms of more than one electron.
Slide 15
Electron Cloud Model By 1926, the electron cloud model had been
created. An electron cloud is the area around the nucleus where its
electrons are most likely to be found. The position of electrons in
the cloud can only be described by a probability.
Slide 16
Neutron - The Final Particle The final subatomic particle was
discovered in 1932. James Chadwick discovered a particle with no
charge but nearly equal mass to the proton. The neutron is located
in the nucleus with the protons. A neutron is a combination of a
proton and an electron
