AQA · Chemistry · 8462
GCSE Chemistry (AQA): The History of the Atom
Topic 1 — Atomic Structure & the Periodic Table. Generated from the caption track of Cognito's lesson video "GCSE Chemistry - The History of the Atom | Models & Theories (2027/28 exams)"; each card deep-links to the moment in the video it came from. Lesson 1.08 of Cognito's AQA GCSE Combined Science (Trilogy) and Chemistry course (Higher tier), filed under AQA Chemistry 8462. Teaching by Cognito — https://cognitoedu.org/coursesubtopic/c2-gcse-aqa-h-c_1.08.
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Who proposed the plum pudding model, and in what year?
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J.J. Thomson, in 1897.
Further experiments by Rutherford showed the positive charge of the nucleus is made of discrete particles called ?.
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protons
How did Niels Bohr's 1913 model prevent the atom from collapsing?
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Electrons orbit the nucleus in fixed shells, much like planets orbit the Sun; the orbiting stops them falling into the nucleus.
What was the key flaw in Rutherford's nuclear model?
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Nothing stopped the cloud of electrons from being pulled into the positive nucleus, so the atom should collapse.
What did Rutherford's nuclear model propose about positive charge?
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That all the atom's positive charge is concentrated in a compact central nucleus, with negative charge in a cloud around it.
Who provided evidence for neutral particles in the nucleus?
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James Chadwick, whose work established the neutron.
How did John Dalton describe atoms in the early 1800s?
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As solid spheres, with a different type of sphere making up each element.
J.J. Thomson's experiments showed that atoms are not solid spheres because they contain negatively charged particles now called ?.
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electrons
What did Rutherford's team fire at a thin sheet of gold in 1909?
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Positively charged alpha particles.
What result of the alpha scattering experiment disproved the plum pudding model?
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Some alpha particles were deflected sideways and a small number bounced straight back, so the positive charge could not be spread out.
Describe the plum pudding model of the atom.
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A ball of positive charge with discrete negative electrons embedded within it.
Which ancient Greek philosopher first proposed atomic theory around 500 BC?
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Democritus. He argued that matter is made of tiny indivisible particles separated by empty space.
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