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. Thomson’s 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.

 

 

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 Rutherford’s 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. Thomson’s 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.

 

 

 

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 Rutherford’s model of the atom, explaining the experiments that led to it