Why are the results of Rutherford's gold foil experiment more consistent with a nuclear model of the atom than with the chocolate chip cookie dough model?

Answer 1

This may start you on the path. It is a simple explanation I developed for a 5th-grade lesson on how scientists use similes. At the time Rutherford was working, scientists had discovered that there were two parts of an atom: protons and electrons. They also knew that protons were much bigger than electrons. A scientist named Thomsen said he thought atoms were like chocolate chip cookies. The protons were like cookie dough, and electrons were mixed in like Chocolate Chips. Rutherford decided to test this idea. He said that if atoms were like Chocolate Chip Cookies, you could make a wall of atoms - like you could built a wall of chocolate chip cookies -- and shine a beam like a light through them, and the beam wouldn't get through. So he tried in an experiment. He didn't use chocolate chip cookies. Instead he used a really thin sheet of gold, made to be as close to one atom thick as he could. But he found out that when he shone the beam at the gold sheet, most of it went straight through the gold and came out the other side. So atoms could not be like chocolate chip cookies. In fact, atoms seemed mostly to be empty space. So Mr. Rutherford tried to imagine what an atom would look like if it were mostly empty space. He thought of another simile. What if atoms were like the solar system? The sun is much bigger than the planets, like protons are much bigger than neutrons. What if atoms were like really tiny solar systems, with electrons orbiting around a clump of protons in the middle? This explanation would match the results of his experiment. Many years later, other experiments have shown similar results. So now, instead of thinking of atoms as chocolate chip cookies, we think of them as tiny solar systems. This answer can be demonstrated by building a wall of cookies with toothpicks. Shine a flashlight, and light will only come through the cracks. However, in Rutherford's experiment, most of the beam (I believe he used gamma rays) went through and hit the reactive film behind the gold. Now imagine a mobile with "suns" made of ping-pong balls and "planets" made of jelly beans set on toothpicks. (I'm not a millionaire. I have to work with the materials I have.) When you shine a flashlight through the "solar systems" of the nuclear model, most of the light goes right through, as they did in Rutherford's experiment with gold. Based on his experiment, Rutherford decided that atoms are not thickly packed together like rows of cookies. Instead, like our solar system, atoms are mostly made up of empty space. Since we are made of atoms, and atoms are mostly empty space, why doesn't light shine through us? The answer is that we are a _lot_ of atoms think. While sun can shine around one leaf, a tree with many leaves arranged in offset layers blocks the light of the sun to create shade. In this example, the leaves are individual atoms, and the many leaves of the tree are like the many atoms in our bodies. This may start you on the path. It is a simple explanation I developed for a 5th-grade lesson on how scientists use similes. At the time Rutherford was working, scientists had discovered that there were two parts of an atom: protons and electrons. They also knew that protons were much bigger than electrons. A scientist named Thomsen said he thought atoms were like chocolate chip cookies. The protons were like cookie dough, and electrons were mixed in like chocolate chips. Rutherford decided to test this idea. He said that if atoms were like chocolate chip cookies, you could make a wall of atoms - like you could built a wall of chocolate chip cookies -- and shine a beam like a light through them, and the beam wouldn't get through. So he tried in an experiment. He didn't use chocolate chip cookies. Instead he used a really thin sheet of gold, made to be as close to one atom thick as he could. But he found out that when he shone the beam at the gold sheet, most of it went straight through the gold and came out the other side. So atoms could not be like chocolate chip cookies. In fact, atoms seemed mostly to be empty space. So Mr. Rutherford tried to imagine what an atom would look like if it were mostly empty space. He thought of another simile. What if atoms were like the solar system? The sun is much bigger than the planets, like protons are much bigger than neutrons. What if atoms were like really tiny solar systems, with electrons orbiting around a clump of protons in the middle? This explanation would match the results of his experiment. Many years later, other experiments have shown similar results. So now, instead of thinking of atoms as chocolate chip cookies, we think of them as tiny solar systems. This answer can be demonstrated by building a wall of cookies with toothpicks. Shine a flashlight, and light will only come through the cracks. However, in Rutherford's experiment, most of the beam (I believe he used gamma rays) went through and hit the reactive film behind the gold. Now imagine a mobile with "suns" made of ping-pong balls and "planets" made of jelly beans set on toothpicks. (I'm not a millionaire. I have to work with the materials I have.) When you shine a flashlight through the "solar systems" of the nuclear model, most of the light goes right through, as they did in Rutherford's experiment with gold. Based on his experiment, Rutherford decided that atoms are not thickly packed together like rows of cookies. Instead, like our solar system, atoms are mostly made up of empty space. Since we are made of atoms, and atoms are mostly empty space, why doesn't light shine through us? The answer is that we are a _lot_ of atoms think. While sun can shine around one leaf, a tree with many leaves arranged in offset layers blocks the light of the sun to create shade. In this example, the leaves are individual atoms, and the many leaves of the tree are like the many atoms in our bodies. Edited to add my information in case someone finds this useful.