PRE-REQUISITES: WHAT DO YOU ALREADY KNOW ABOUT THE TOPIC?
ACTIVITIES AND KEYS LESSON 2
2.1 CLOZE
Fill in the blanks
A large portion of
Rutherford's
. has always included the use and study of alpha particles
ever since he classified them in 1898. Starting sometime around 1909,
Rutherford began to notice that
.. would not always behave in accordance
to the plum pudding model of an atom when
at a piece of gold foil.
These observations stimulated further research that was eventually published in
1911 and has been known ever since as Rutherford's Gold Foil Experiment.
Throughout the course of his experiment, Rutherford and his two associates (Hans Geiger and Ernest Marsden) aimed a .. of alpha particles at a piece of gold foil that was approximately 8.6 x 10-6 cm To be more accurate Rutherford actually included a wide of different foils (such as: aluminium, and lead), but his use of gold foil is most commonly . . In accordance to the J.J. Thomsons model of an atom, the alpha particles should have passed through the gold foil for all instances. Therefore, to confirm this activity, a zinc sulphide screen was placed behind the foil as a backdrop for the alpha particles to appear upon. Directly above this screen was a . that allowed one of the two experimenters (only Geiger and Marsden actually performed the experiment, Rutherford just explained the ) to observe any contact made between the alpha particles and the screen. In order for the light of the alpha particles to be .. , the experiment was performed in complete ... Also, to further enhance the accurateness of the observations the experimenter that was charged with looking through the microscope sat in the dark of the lab room for at least one hour before .. the experiment. This was done in order to allow the experimenter's eyes to reach the .. visual acuity.
Thick observed directly fired research spoken of performing maximum beam darkness alpha particles microscope variety results iron
2.2 CLOZE
Fill in the blanks
After the experiment had
been
. in accordance to the speculations described above, Geiger and
Marsden would fire the beam of alpha particles through the piece of foil and
observe the
. at which the particles landed on the screen. As
explained above, each particle should have gone directly through the foil if
the plum pudding model was
. (meaning that an atom was a vast amount of
.. space and could easily be passed through by
particle).
For the most part, the alpha particles
.. with this hypothesis and
passed straight through the gold foil. There were, however, a small
..
of particles that deflected slightly from the straight path by about one or two
degrees. But the biggest discovery was made when 1 in 20,000 particles would
. approximately 90
or more from the parent beam. In fact,
an
.. particle even fired right back at the experimenter. Perhaps
Rutherford described the awe-inspiring nature of the discovery
.. when
he said: "It was as if you fired a 15-inch shell at a sheet of tissue
paper and it came back to hit you."
The results of this
experiment gave Rutherford the means to arrive at two conclusions: one, an atom
was much more than just empty space and
electrons (J.J. Thomson model
argued for), and two, an atom must have a
.. charged centre that
contains most of its
.. (which Rutherford termed as the nucleus).
Since alpha particles are relatively heavy, positively charged particles, the
fact that the occasional particle would be deflected by either a small or large
margin proved that a portion of an atom was both positively charged (particles
of identical charges repel one another while particles of opposite charges
attract one another) and relatively
. by atomic
.. . Since
only a small number of alpha particles veered slightly when passed through the
foil and since even fewer
at the experiment, Rutherford reasoned
that this positively charged centre was relatively small in
. to the
total size of the atom. Therefore, J.J. Thompson was slightly correct in his
assumption that atoms are primarily composed of empty space.
Given below is an
illustration that compares the plum pudding model of an atom to what Rutherford
observed in his experiment. The top picture shows how the alpha particles would
have passed through the gold foil atoms if the plum pudding model was
..in its assumptions. The bottom picture shows what Rutherford and his
colleagues observed and is the true
.of an atom's structure.
_file/image002.gif)
Location empty heavy correct Χ2 set up occasional scattered depiction mass handful bounced back reference best corresponded positively degrees any deflect standards
2.3 CLOZE
Fill in the blanks
With the disproof of the
plum pudding model and with Rutherford's discovery of an atom's
., it
was now possible for Niels Bohr to construct his
model of an atom's
. . Bohr conversed with Rutherford on several
occasions and was able to use the knowledge he gained from the encounters to
create what is now called the
. model of an atom. To explain
briefly, Bohr described the
.. atom as a nucleus with an electron
around it, much as a planet orbits the sun. The problem with Bohr's
model is that it only works
. for the hydrogen atom. Even though
Bohr's model was not entirely correct in its application, the point to grab
here is that Rutherford's experiment with gold foil and his discovery of the
. gave a huge
.. to the development of today's atomic
theory(s). Yes, another scientist probably would have made the same discovery
given the opportunity of a few years, but Rutherford had the intelligence and
the
. to put the ideas together when he did. Essentially, putting
ideas together is really what
is all about.
Soundly hydrogen science quantum mechanical nucleus Χ2 circling insight structure - contribution
http://myweb.usf.edu/~mhight/goldfoil.html
2.4 SUMMARY
Describe the main features of Rutherfords model of
the atom, explaining the experiments that led to it
PRE-REQUISITES: WHAT DO YOU ALREADY KNOW ABOUT THE TOPIC? (A CURA DELLO STUDENTE)
2.1 CLOZE
KEY
Fill in the blanks
A large portion of Rutherford's research has always included the use and study of alpha particles ever since he classified them in 1898. Starting sometime around 1909, Rutherford began to notice that alpha particles would not always behave in accordance to the plum pudding model of an atom when fired at a piece of gold foil. These observations stimulated further research that was eventually published in 1911 and has been known ever since as Rutherford's Gold Foil Experiment.
Throughout the course of his experiment, Rutherford and his two associates (Hans Geiger and Ernest Marsden) aimed a beam of alpha particles at a piece of gold foil that was approximately 8.6 x 10-6 cm thick To be more accurate Rutherford actually included a wide variety of different foils (such as: aluminium, iron and lead), but his use of gold foil is most commonly spoken of. In accordance to the J.J. Thomsons model of an atom, the alpha particles should have passed directly through the gold foil for all instances. Therefore, to confirm this activity, a zinc sulphide screen was placed behind the foil as a backdrop for the alpha particles to appear upon. Directly above this screen was a microscope that allowed one of the two experimenters (only Geiger and Marsden actually performed the experiment, Rutherford just explained the results) to observe any contact made between the alpha particles and the screen. In order for the light of the alpha particles to be observed, the experiment was performed in complete darkness. Also, to further enhance the accurateness of the observations the experimenter that was charged with looking through the microscope sat in the dark of the lab room for at least one hour before performing the experiment. This was done in order to allow the experimenter's eyes to reach the maximum visual acuity.
Thick observed directly fired research spoken of performing maximum beam darkness alpha particles microscope variety results iron
2.2 CLOZE
KEY
Fill in the blanks
After the experiment had been set up in accordance to the speculations described above, Geiger and Marsden would fire the beam of alpha particles through the piece of foil and observe the location. At which the particles landed on the screen. As explained above, each particle should have gone directly through the foil if the plum pudding model was correct (meaning that an atom was a vast amount of empty space and could easily be passed through by any particle). For the most part, the alpha particles correspondent with this hypothesis and passed straight through the gold foil. There were, however, a small handful of particles that deflected slightly from the straight path by about one or two degrees. But the biggest discovery was made when 1 in 20,000 particles would deflect approximately 90 degrees or more from the parent beam. In fact, an occasional particle even fired right back at the experimenter. Perhaps Rutherford described the awe-inspiring nature of the discovery best when he said: "It was as if you fired a 15-inch shell at a sheet of tissue paper and it came back to hit you."
The results of this experiment gave Rutherford the means to arrive at two conclusions: one, an atom was much more than just empty space and scattered electrons (J.J. Thomson model argued for), and two, an atom must have a positively charged centre that contains most of its mass (which Rutherford termed as the nucleus). Since alpha particles are relatively heavy, positively charged particles, the fact that the occasional particle would be deflected by either a small or large margin proved that a portion of an atom was both positively charged (particles of identical charges repel one another while particles of opposite charges attract one another) and relatively heavy by atomic standards . Since only a small number of alpha particles veered slightly when passed through the foil and since even fewer bounced back at the experiment, Rutherford reasoned that this positively charged centre was relatively small in reference to the total size of the atom. Therefore, J.J. Thompson was slightly correct in his assumption that atoms are primarily composed of empty space.
Given below is an illustration that compares the plum pudding model of an atom to what Rutherford observed in his experiment. The top picture shows how the alpha particles would have passed through the gold foil atoms if the plum pudding model were correct in its assumptions. The bottom picture shows what Rutherford and his colleagues observed and is the true depiction of an atom's structure.
_file/image003.gif)
Location empty heavy correct Χ2 set up occasional scattered depiction mass handful bounced back reference best corresponded positively degrees any deflect standards
2.3 CLOZE
KEY
Fill in the blanks
With the disproof of the plum pudding model and with Rutherford's discovery of an atom's nucleus, it was now possible for Niels Bohr to construct his model of an atom's structure. Bohr conversed with Rutherford on several occasions and was able to use the knowledge he gained from the encounters to create what is now called the quantum mechanical model of an atom. To explain briefly, Bohr described the hydrogen atom as a nucleus with an electron circling around it, much as a planet orbits the sun. The problem with Bohr's model is that it only works soundly for the hydrogen atom. Even though Bohr's model was not entirely correct in its application, the point to grab here is that Rutherford's experiment with gold foil and his discovery of the nucleus gave a huge contribution to the development of today's atomic theory(s). Yes, another scientist probably would have made the same discovery given the opportunity of a few years, but Rutherford had the intelligence and the insight to put the ideas together when he did. Essentially, putting ideas together is really what science is all about.
Soundly hydrogen science quantum mechanical nucleus Χ2 circling insight structure - contribution
http://myweb.usf.edu/~mhight/goldfoil.html
2.4 SUMMARY (A CURA DELLO STUDENTE)
Describe the main features of Rutherfords model of the
atom, explaining the experiments that led to it