History of atomic theory

High school (ages 12+)
Science & Technology

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Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/history-of-atomic-theory

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the philosophical precursor?Democritus's concept of 'atomos' (uncuttable particles) in Ancient Greece (c. 400 BCE)
2. What is the nuclear model?Ernest Rutherford's experiments revealed a dense, positively charged nucleus (1911)
3. What is an atom?An atom is the tiniest piece of matter that makes up everything around us. It was first imagined by ancient Greek philosophers as a tiny, unbreakable ball.
4. Why did scientists change their idea of atoms after discovering electrons?The discovery of the electron showed that atoms are not indivisible. Scientists had to revise their models to include these smaller, negatively charged particles.

Atomos: Ancient Greek term for indivisible particles, meaning 'uncuttable'.
Law of Definite Proportions: A chemical compound always contains its component elements in a fixed ratio by mass.
Cathode Ray: A stream of electrons emitted from the negative electrode in a vacuum tube.
Quantized Energy Levels: Specific, discrete amounts of energy that electrons can possess within an atom.