NAME:
DATE:
CLASS PERIOD:
TOPIC: CH. 14: Inside the Atom
Section 1: Models of the Atom
*Main Idea (p. 402):
Important Terms:
Atom: A unit of matter, the smallest unit of an element.
Element (p. 405):
Compound: (p. 473):
Periodic table: The periodic table is a tabular arrangement of the
chemical elements, organized on the basis of their atomic
numbers, electron configurations, and recurring chemical
properties.
Anode (p. 405):
Cathode (p. 406):
Electron (p. 407):
Proton (p. 410):
Neutrons (p. 411):
Electron Cloud (p. 413):
Atom Launch Lab:
Directions:
1. Pass around the ball of playdoh to each member of the group.
As you pass it, each member will take a small amount from the
ball and place it on their paper towel. The person who started the
passing will hold onto the main portion given, but put it to the
side.
2. Once you have taken of a small chunk, think about this. Could
you break that little piece even smaller? What is the piece
COMPOSED of? TALK THIS OVER WITH YOUR GROUP, and
come up with an answer.
Even the smallest amount of playdoh contains atoms. There are
atoms in everything. We see objects, and these objects contain
atoms that we can’t see even with a microscope. In 1981, a
scanning tunnel microscope (STM) was invented that allows
scientists to send an electric current into a sample using a probe.
When it encounters an atom, it registers (or shows up) on a
scanner.
4. The ingredients of playdoh are:
-water
-salt
-wheat flour
-petroleum- to keep it smooth
-borax-to keep it from getting moldy
-Let’s take a look at the periodic table, so we can point out a few
of these items.
5. Where you able to locate salt and water on the periodic table?
Why or why not?
6. What is the chemical code for water?
7. What is the chemical code for salt? NaCl
8. Are these elements or compounds?
Reading Ch. 14, Section 1: Models of the Atom (pp. 404-413)
NOTES:
First Thoughts:
People began wondering about matter more that ________ years
ago.
Atom is a term that means “ ____________________.”
If you keep dividing a string into pieces, you eventually come to a
___________ ___________.
Describing the Unseen:
Today, scientists will not accept a theory that is not supported by
experimental ___________________.
Even as recently as 500 years ago, atoms were still a
______________.
A Model of the Atom:
During the 18th century, scientists in laboratories began debating
the existence of ___________once more.
Chemists were
________________________________________________.
They were putting substances together to forms new
____________ and taking substances apart to find out what
they were __________ of.
Iron is made of ____________ ____________. Silver is made
of ___________ __________.
_____________, _____________, and ___________ are
other examples of elements.
Dalton’s Concept:
He proposed the following ideas about matter:
1.
2.
3.
4.
Scientific Evidence:
A Strange Shadow:
Draw a quick sketch of Crooke’s glass tube experiment.
Cathode Rays:
Reading Check: What are cathode rays?
Discovering Charged Particles:
Many scientists were not convinced that the cathode rays were
streams of _____________.
Light cannot be bent by a ___________, so the beam couldn’t be
light.
J.J. Thomson, an English physicist, concluded that the beam must
be made up of charged _________________ of
_____________that came from the cathode.
The Electron
Thomson’s research led to the discovery of _____________.
Perhaps the biggest surprise that came from Thomson’s
experiments was the evidence that ________________ smaller
than the ______________ do exist.
Thomson’s Atomic Model:
Thomson included a ___________ charge in his model of an
_________.
Not all atoms are _____________. The number of electrons
within an element can vary. If there is more _____________
charge than negative ______________, the atom has an overall
positive _______________. If there are more negative
electrons than positive charge, the atom has an overall
____________ charge.
Reading Check: What particle did Thomson’s model have
scattered through it?
Rutherford’s Experiments:
Ernest Rutherford and his coworkers began an experiment to find
out if Thomson’s model of the atom was ________________.
They wanted to see what would happen when they fired fast
moving, positively charged bits of matter, called
_______________ ______________, at a thin film of metal
such as gold. ________________ ______________, which
come from unstable atoms, are positively charged, and so they
are ______________ by particles of matter which also have a
positive charge.
Expected Results:
His prediction was that most of the speeding alpha particles
would pass right through the __________ and hit the screen on
the other side. Rutherford was so sure of what his results would
be that he
_______________________________________________.
The Proton
Rutherford hypothesized that almost all of the mass of an atom
and all of its positive charge are crammed into an incredibly small
region of space at the center of the atom called the
__________________.
Eventually, his prediction was proven ______________.
Most alpha particles could move through the foil with little or no
__________________ because of the empty space that makes
up most of the atom.
However, if an alpha particle made a direct hit on the nucleus of a
gold atom, which has ______protons, the alpha particle would be
strongly ______________ and ___________ ___________.
The Neutron:
What new question did Rutherford’s model leave with scientists?
It was proposed that another particle must be in the
___________ to account for the extra mass.
The particle, which was later called the _______________,
would have the same mass as a proton and be electrically
_______________.
Proving the existence of the neutrons was difficult though,
because the neutron has no __________________.
Therefore, the neutron doesn’t respond to _____________ or
cause fluorescent screens to _______________ _________.
Reading Check: What particles are in the nucleus of the nuclear
atom?
Negatively charged _____________ occupy the space
surrounding the nucleus. The number of electrons in the neutral
atom equals the number of _______________ in the atom.
Size and Scale
After examining Figure 13, why did most of the alpha particles in
Rutherford’s experiment go directly through the gold foil without
any interference from the gold atoms?
Further Developments
Even into the 20th century, physicists were working on a theory to
explain how _______________ are arranged in the atom.
Scientists determined that it was impossible to know the precise
______________of an ____________ at any particular
moment.
The Electron Cloud Model
Although scientists don’t know exactly where in the atom
electrons can be found, they are most likely traveling in a region
close to the nucleus, known as the ____________ _________.
Let’s compare the three viewpoints on Atoms:
Dalton (description and picture)
Thomson (description and picture)
Rutherford (description and picture)