Chemistry and the Atom

A Level Investigations What sorts of discoveries have been made about atomic structure? How was the size of an atom’s nucleus determined? What are atoms and how are they put together? What does atomic structure have to do with the periodic table?

Atomic Structure What sorts of discoveries have been made about atomic structure? Ernest Rutherford

Research these scientists Democritus John Dalton J.J. Thomson Ernest Rutherford Niels Bohr Louis de Broglie Erwin Schrodinger James Chadwick Albert Einstein

How was the size of an atom’s nucleus determined? Key Question How was the size of an atom’s nucleus determined?

History of Atomic Theory Atom Game has a short history of the atomic theory enclosed in pamphlet in box. Teaching Tip: Xerox history and place in plastic sleeves for reference, short classroom presentations, projects or reading assignments.

Materials Circle templates (3) sizes: Carbon paper Metric ruler one per student, random three groups, each with same template three per group Carbon paper Metric ruler Steel marble Hard surface

Procedure Place carbon paper face up on table. Turn over the template and tape it onto the table. Each person drops marble randomly all over the paper. Allow only ONE strike- COUNT each strike on the paper- total 100 strikes.

Data Calculation of total area of circles

Measure How do we determine the total area of the paper? A = L x W

Indirect Measurement We need to determine the area of ONE circle. How do we do this?

Analyzing Results- Step a Divide the total area of the circles by the number of circles on your paper. This will tell you the area of ONE circle by indirect measurement.

Sample Data 1.0 cm = 148 circles 1.5 cm = 88 circles

Rutherford’s experiment When Rutherford and his colleagues did this experiment, they counted the alpha particles that went through the foil and the alpha particles that bounced back. They also knew the total number of alpha particles — it simply meant adding the number that went through to the ones that bounced back.

Rutherford’s experiment Rutherford also knew the total area of the gold foil. He could use these three pieces of information to set up a proportion: A = C B D

Rutherford’s Experiment The equation that Rutherford and his colleagues used to determine the diameter of the nucleus of an atom: A = total number of α particles that bounced back B = total number of α particles C = total area of the part of atoms that blocked α particles D = total area of gold foil A = C B D

Direct Measurement How can we determine the area of ONE circle? What information do we know/need? A = p r2

Analyzing Results- Step b To find the area of our circles using the radius we just measured: A = p r2 Compare this value with the area found by the indirect method. Calculate the percent error of your results.

Drawing Conclusions The marble represents the alpha particles, whereas the paper represents the gold foil. The carbon paper represents the screen that was used to detect the alpha particles. Dropping the marble represents bombarding the nuclei in the gold foil.

Subatomic Particles What three basic particles make up all atoms?

Can you guess which marble represents which particle? Everyone will guess that the small yellow marbles are electrons, which is correct. The electron is represented with a small marble because it contributes almost no mass to the atom. However, no one will know for sure which particle goes with red and blue marbles, since they are the same size and protons and neutrons contribute equally to the mass of the atom.

Take turns building atoms. To complete your turn…

WRITE OR RECITE: Remember to follow these rules when building atoms! If another player challenges your atom, and if your atom is indeed incorrect, you must remove all marbles on the board and put them in your board pocket! If the challenger is wrong, that player loses a turn. You can trade marbles with the bank if you want to skip a turn. The number you put in the bank must equal the number you take back out, but the colors can be different. You may stop here if necessary. Up to this point, the workshop should take about 30 min.

H Hydrogen What is the symbol for hydrogen? What is the atomic number? How many hydrogen atoms are stable? How many neutrons can hydrogen have? H 1,2 1

Write on a blank table or recite: Practice Write on a blank table or recite: This element is atomic number _____, so it has _____ protons. There is/are ___ neutron(s) There is/are ___ electron(s) It’s name is _________ - ___

Hydrogen - 1 Try to make helium-3 What should you write/recite? This atomic number is 1, so it has ONE proton. There is NO neutron. There is 1 electron. It’s name is hydrogen- 1 Try to make helium-3

He Helium-3! What should you write/recite? 3,4 2 This atomic number is ___, so it has ____ protons. There are ___ neutrons. There are ___ electrons. It’s name is ___________ - ____ 3,4 He 2

Build the first ___ atoms

FOLLOW: Remember to follow these rules when building atoms! If another player challenges your atom, and if your atom is indeed incorrect, you must remove all marbles on the board and put them in your board pocket! If the challenger is wrong, that player loses a turn. You can trade marbles with the bank if you want to skip a turn. The number you put in the bank must equal the number you take back out, but the colors can be different. You may stop here if necessary. Up to this point, the workshop should take about 30 min.

The game of Atomic Challenge 4-8 players or teams per board Start with 6 blues, 5 reds, and 5 yellows in each board corner. Each player takes turns adding marbles to the atom (up to 5 per turn) to make stable, neutral atoms. The first player to lose all their marbles wins!!! Now that we know how the model is set up, let’s apply our knowledge of atomic structure. Note: To play longer game, add 2 marbles of each kind to board Here are the rules of the game called “Atomic Challenge”

Remember to follow these rules when building atoms Remember to follow these rules when building atoms! If another player challenges your atom, and if your atom is indeed incorrect, you must remove all marbles on the board and put them in your board pocket! If the challenger is wrong, that player loses a turn. You can trade marbles with the bank if you want to skip a turn. The number you put in the bank must equal the number you take back out, but the colors can be different. You may stop here if necessary. Up to this point, the workshop should take about 30 min.

What is an ISOTOPE? Different “versions” of the same element can be found in nature. Some have a stable nucleus and some do NOT. Some are more common in nature. They are named according to their mass number: hydrogen - 1 hydrogen - 2

Nuclear Particle Cards Red, yellow and blue marbles in corners. 4 players or teams per board Shuffle cards and deal 5 per player On each turn, play a card and add or take particles as the card instructs On some turns you will score points; on other turns you will not (you may be blocking an opponent) Now we will advance one step further, and play another version of the atom building game, this time using the nuclear reaction cards. The rules for playing this game are on this slide See next slide for a summary of how points are scored

Create or leave a neutral atom, you score 1 point Scoring Points: Create or leave a neutral atom, you score 1 point Creates or leave a stable nucleus, you score 1 point Create a neutral atom with a stable nucleus, you score 3 points First person to 15 points wins! It is important to note that in this game, you don’t have to build a perfect atom to score points. You can score 1 point if you achieve a stable nucleus, even if the number of protons and electrons are not equal. You can also score 1 point if you achieve a neutral atom, even if the nucleus does not contain a number of neutrons that would represent a stable isotope. However, if you DO achieve a perfect atom in one turn, you can score 3 points. Of course, if you inherit a stable nucleus from the previous player, and you just make the protons and electrons equal each other, you will leave a perfect atom after your turn and you can score all 3 points!!! You might want to put the Atom Building Reminders slide back up so people can refer to it

What is an ion? A different “version” of an atom that is NOT neutral. Some ions are more common in nature. What do ions have to do with Chemistry?

Modifications/Extensions Alternative Assessments Rotation Game Overhead Quizzes Station Quizzes Glue Gun option Nuclear Particle Cards

Making Atoms Build the 6 atoms shown on the chart and fill in the missing information.

Making Atoms