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Atomic Theory

Part 3: The Nucleus and The Neutron . Atomic Theory. The Story So Far. But wait…. What is the fundamental problem with this idea?? Why don’t the electrons spiral right into the nucleus ?. But wait….

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Atomic Theory

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  1. Part 3: The Nucleus and The Neutron Atomic Theory

  2. The Story So Far

  3. But wait…. What is the fundamental problem with this idea?? Why don’t the electrons spiral right into the nucleus ?

  4. But wait…. • After many years of research, the positive charge in atoms’ nuclei was identified as a particle called the “proton” • But, there had to be something else in the nucleus…otherwise why wouldn’t the protons be repelled from each other?

  5. The neutral particle… • In 1932 (20 yrs after Bohr discovered electron shells), James Chadwick (another Brit), proved that neutral particles existed • These were called “neutrons” • He was awarded the Nobel Prize, too

  6. The Neutron • The neutron is neutral • It has no charge • Neutrons in the nucleus prevent the protons from repelling each other • Like charges repel (+ +, or - -), and unlike charges attract (+ -)

  7. But Wait… • There’s another fundamental problem: • Hint: unlike charges attract • Why don’t the negative electrons collapse into the positive nucleus?

  8. What Prevents Electrons and Protons from Colliding? A few things: Distance of electrons from the nucleus The atom is made up mostly of empty space A hydrogen atom is only about a ten millionth (1/10000000) of a millimeter in diameter, but the proton in the middle is a hundred thousand times smaller (1/1000000000000), and the electron whizzing around the outside is a thousand times smaller than THAT (1/100000000000000000). The rest of the atom is empty

  9. What Prevents Electrons and Protons from Colliding? • In other words, electrons are REALLY far away from the positive nucleus! • If the nucleus was the size of a grape, then electrons in the first energy shell would be 1.6 km away! 3.2 km

  10. Centrifugal force As electrons orbit the nucleus of an atom, they spin This spinning creates a force known as centrifugal force, which pushes the particle away from the center of its orbit This means that the electron particle will not collide with the proton, even with an electric attraction What Prevents Electrons and Protons from Colliding?

  11. Centrifugal force * Centrifugal force: the tendency of an object following a curved path to fly away from the center

  12. Electrons are funny and do not obey ordinary physical laws Therefore cannot be assumed to obey the rules of attraction of oppositely charged particles What Prevents Electrons and Protons from Colliding?

  13. Recap 3 things prevent electrons and protons from colliding Distance between them is huge Centrifugal force works against electric charge attraction Electrons are funny

  14. The 3 Subatomic Particles

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