Chem Unit 1 Summative Exam CER Portion

​Unit 1 Summative Exam
CER Portion

By En-Tze Chong

Anti-cheating Enabled

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Open Ended

Neils Bohr's  experiments showed that each element always emitted the same wavelengths of light when excited with electricity.  He used this data to create a new atomic model that showed different levels of electron orbitals around each atom.  The previous model (Ernest Rutherford's model) believed that electrons traveled in specific circular paths around the nucleus.  If Rutherford's model was correct, it would predict random wavelengths of light to come out of each atom or element.  Instead, Bohr's experiment showed that there must be something unique to each electron's orbital energy level.

Describe Niels Bohr's Claim, Evidence, and Reasoning.

Your answer should include the name of the atomic model, any new subatomic particles discovered, the scientist's experiment, and describe what kind of evidence would prove that their theory is inaccurate

Open Ended

In 1932, James Chadwick discovered the neutron, which became a turning point in nuclear physics. Before this, scientists only knew of two particles in the atom: protons, which are positively charged, and electrons, which are negatively charged. Some scientists, like Ernest Rutherford, had guessed there must also be a neutral particle to explain why the mass of certain atoms, like helium, didn’t match what they expected.

Chadwick’s investigation built on earlier findings. Researchers had noticed that when high-energy alpha particles hit elements such as beryllium, the collision produced a new type of radiation. At first, some thought this radiation was just high-energy gamma rays, but the evidence didn’t fit. Chadwick set up an experiment where he fired alpha particles at beryllium, which released this mysterious radiation. He then placed a layer of paraffin wax in the path of the radiation. Surprisingly, the radiation knocked protons out of the paraffin. Since gamma rays couldn’t knock protons out like that, Chadwick concluded that the radiation had to be made of a new particle with mass but no charge — the neutron.

This discovery proved that the nucleus contains both protons and neutrons. It also introduced the idea of nuclear forces, a new type of force different from gravity and electromagnetism. Chadwick’s work explained isotopes and later made nuclear fission possible. His discovery opened the door to the atomic age, which brought huge changes for both science and society.

Please describe James Chawick's Claim Evidence and Reasoning

Your answer should include the name of the atomic model, any new subatomic particles discovered, the scientist's experiment, and describe what kind of evidence would prove that their theory is inaccurate