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Modern Model of the Atom

Modern Model of the Atom. From Bohr to Today. Note to Reader. Words in bright pink are notes from the teacher to help you understand the material. IF you are writing this down instead of printing it, these do not need to be copied. Neils Bohr’s Model.

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Modern Model of the Atom

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  1. Modern Model of the Atom From Bohr to Today

  2. Note to Reader • Words in bright pink are notes from the teacher to help you understand the material. IF you are writing this down instead of printing it, these do not need to be copied.

  3. Neils Bohr’s Model • The electrons must be in a fixed orbit around the nucleus. • Each orbital has its own specific energy level. • No electrons can exist in between the energy levels. • But remember, this only worked for Hydrogen.

  4. Heisenberg and Schrodinger • Realized that electrons are not completely described as small particles but that they can have both wave and particle properties. • This means that electrons were behaving a little like light and a little like matter.

  5. Heisenberg’s Uncertainty Principle • On the scale of atomic particles, we cannot determine exactly the position, direction of motion, and speed all at the same time. • Also restated as “The behavior of particle is affected by the act of observing the particle. Therefore, by observing it you have changed something about it.”

  6. Schrodinger • Determined an equation to give the probability of finding an electron in a given area, which he named ‘Orbitals.’ • These orbitals provide the electron density distributed about the nucleus. • Orbitals are described by quantum numbers.

  7. Quantum Mechanical Model • Does not describe the movement of the electrons, only where they are most likely found any point in time. • Orbital – a region in which an electron will have the greatest probability of being found. (Any orbital can hold two electrons.)

  8. Quantum Numbers • Set of 4 numbers describes everything you need to know to find an electron within a specific atom. (Tells its address.)

  9. For Example • In order to tell someone where you live, you need to give them four pieces of information. • What state you live in • What city you live in • What street you live on • What the house number is • Without all four pieces of information, the person will not be guaranteed to find your house. It is the same with an electron… we need to be given four pieces of information to find it.

  10. Principle quantum number (N) • Tells the distance from the nucleus; the main energy level (Like the state in your address) • Numbers 1-7 (shell 1 is close to the nucleus and shell 7 is far) • Corresponds to rows on the periodic table and the rings in Bohr’s model.

  11. Principle Energy Level 1 2 3 4 5 6 7

  12. So… • Hydrogen has one electron in principle energy level 1. • Calcium has 20 electrons. • 2 are in PE 1 • 8 are in PE 2 • 8 are in PE 3 • 2 are in PE 4 2 1 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 2 1

  13. Orbital Quantum Number (l) • Tells the shape of the orbit. • (Like the city in your address). • As you move up principle energy levels, you can add one more type of orbit. • (Kind of like if you have a small city, it doesn’t have many restaurants, but the larger it gets, the more kinds it will have.)

  14. Orbital Quantum Number • S shape – 1 in every principle energy level, holding 2 electrons each • P shape – 3 total in every PE level starting with level 2 (Each level will have one of each “version” below. Remember, each of the orbits holds 2 electrons, so the p shape holds a total of 6 electrons in any principle energy level)

  15. Orbital Shapes Continued • d – 5 total in every PE starting with level 3(5 orbits with 2 electrons each = 10 electrons) • f – 7 total in every PE starting with level 4 (the pictures get very complicated here, you don’t need to know what an f orbital looks like) 4 of this type 1 of this type

  16. Finding Orbital Quantum #s on the Periodic Table P Block S Block D Block F Block

  17. Magnetic Quantum Number • Tells the position in space. • (Like the street name in your address). • Since there are three different versions of p orbits, this tells us which version we are talking about. Is it the one that is oriented on the x axis, the y axis or the z axis. (We will not be designating these with actual numbers this year.)

  18. Spin Quantum Number • Tells the direction of spin of the electron. • (Like the house number in your address.) • Pauli Exclusion Principle: No two electrons can have the same of Quantum Numbers. • For the two electrons that exist in the same principle energy level, in the same shape, in the same orientation, the two electrons spin in opposite directions. • If you live in the same state, city and street as your friend, you have to have different house numbers to tell them apart.

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