How Chadwick Discovered the Neutron in 1932

​Sources for this Quizizz Lesson:

• https://www.britannica.com/biography/James-Chadwick

• https://www.pbs.org/wgbh/aso/databank/entries/dp32ne.html

• https://www.electrical4u.com/rutherfords-atomic-model/

​You will have a reading passage on tomorrow's test. Today, we will practice reading and analyzing a nonfiction scientific text.

How Chadwick Discovered the Neutron in 1932

During World War I, James Chadwick was interned in a civilian prisoner-of-war camp in Germany. He was imprisoned for being a British citizen studying in Germany when the war began. While in the prison camp, he conducted scientific experiments using improvised materials within the camp.

Poll

Which trait did Chadwick demonstrate by conducting scientific experiments while interned in a prisoner-of-war camp.

• Prompt

• Polite

• Perseverance

• Prepared

When World War I ended, Chadwick returned to his native England to rejoin the mentor of his undergraduate days, Ernest Rutherford. Now head of Cambridge University's nuclear physics lab, Rutherford oversaw Chadwick's PhD in 1921 and then made him assistant director of the lab.

Prior to 1921, Rutherford had made big advances in scientists' understanding of the atom. Rutherford was a student of JJ Thomson, who was famous for proposing the “plum pudding model” of the atom.

Rutherford tested Thomson’s model of the atom with his “Gold Foil Experiment.”

In his experiment, Rutherford observed that most of the alpha particles went straight through the gold foil. Only a few of the particles bounced back or scattered at different angles. This proved to Rutherford that an atom is mostly empty space.

Multiple Choice

What conclusion did Rutherford make based on his observation that most of the alpha particles went straight through the gold foil?

• Protons are negatively charged.

• An atom is mostly empty space.

• Electrons repel alpha particles.

• There are protons and neutrons in an atom.

Rutherford's gold foil experiment also proved that an atom has a small, dense, positively charged nucleus at its center, which is surrounded by mostly empty space where electrons orbit. He disproved the previously held "plum pudding model" of the atom and established the nuclear model of the atom.

Rutherford had discovered the proton, a positively charged particle within the atom's nucleus.

Drag and Drop

Rutherford was able to disprove Thomson's plum pudding model through ​

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. This new evidence changed how we understand the ​

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.

Drag these tiles and drop them in the correct blank above

experimentation

guessing

atom

cell

Rutherford, Chadwick and other researchers hypothesized that the proton was not the only particle in the nucleus.

Rutherford thought there could be a particle with mass but no charge. He called it a neutron, but there was no evidence for any of these ideas.

Chadwick kept the problem in the back of his mind while working on other things. Experiments in Europe caught his eye, especially those of Frederic and Irene Joliot-Curie. They created radioactive isotopes by bombarding stable elements with alpha particles.

Chadwick repeated their experiments but with the goal of looking for a neutral particle - one with the same mass as a proton, but with zero charge. His experiments were successful. He was able to determine that the neutron did exist and that its mass was about 0.1 percent more than the proton's.

Multiple Select

What TWO connections can you make between this article about Chadwick and the nature of science?

• a scientist's hypothesis is always wrong

• scientists share information & data with each other

• new evidence is used change and update models and theories

• old theories become new laws

Chadwick published his findings with characteristic modesty in a first paper entitled "Possible Existence of Neutron." In 1935, he received the Nobel Prize for his discovery.

​Sources:

• https://www.britannica.com/biography/James-Chadwick

• https://www.pbs.org/wgbh/aso/databank/entries/dp32ne.html

• https://www.electrical4u.com/rutherfords-atomic-model/

Multiple Select

What TWO conclusions can you make based on this article?

• Scientists guess when they create models.

• Models of atoms have benefits and limitations.

• There is nothing new to discover about atoms.

• Atomic models changed over time because of new discoveries.