The nuclear atom, nuclides, isotopes and ions
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 1 worked example, 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Mostly empty space
- The scattering experiment
- What it showed
Read the transcript of the teaching part
Last time
Before we start: last time, in The transformer and the oscilloscope, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Mostly empty space
Everything you touch is made of atoms, and each atom is almost entirely empty space. If the nucleus were a marble on the centre spot of a football pitch, the electrons would be at the edge of the stands. How do we know this? Because over a hundred years ago, two scientists fired tiny particles at gold, and looked at what bounced back.
The scattering experiment
A beam of alpha particles was fired at a very thin sheet of gold foil, in a vacuum. A detector counted the particles that came out at different angles. Most passed straight through. A few were deflected through large angles. Very few bounced almost straight back.
What it showed
Most alpha particles went straight through, so an atom is mostly empty space. A few were deflected, so they were repelled by a small, positively charged centre. Alpha particles are positive, and like charges repel. Very few bounced back, so the nucleus is very small and contains most of the mass of the atom.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Nuclide notation and isotopes · Rutherford scattering · Alpha-particle scattering · Isotopes · Proton number, nucleon number and nuclide notation · Protons, neutrons and ions.
The whole chapter: The Nuclear Model of the Atom, The Nuclear Model of the Atom.
Chapter 5.1: The nuclear model of the atom
- The nuclear atom, nuclides, isotopes and ions 5 min
Also for O Level Physics 5054
Which topics come up most in O Level Physics 5054 past papers, counted from every paper since 2004.