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Chapter 13 Day 2 Quantum Numbers and Electron Configurations Bono "The less you know, the more you believe."

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Models of the Atom DaltonThomsonRutherfordBohr

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Neils Bohr model of the Atom: Electrons can be in 1 of many principle energy levels, but cannot be in between any of these energy levels. Electrons move around the nucleus like planets move around the sun. Each Principle Energy Level (n) is given a number n=1 n=2 n=3

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Unfortunately, Bohrs model of the Hydrogen atom turned out to be incorrect, so a new model was introduced. Not This! But, This!

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What are the Quantum Numbers? Remember – they give the approximate location of electrons in an atom. Remember – they give the approximate location of electrons in an atom. They are actually represented by letters. They are actually represented by letters. N – distance (size of orbital) N – distance (size of orbital) l – Shape of orbital l – Shape of orbital m – orientation in space of orbital m – orientation in space of orbital s – spin of the electron s – spin of the electron

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Erwin Schrödinger, using complex mathematics, calculated the probability of where an electron is located. The probability of an electron in the first principle energy level: An orbital is drawn that encloses the region where the electron is found 90% of the time.

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First Energy Level (n=1) can contain 1 sublevel orbital Second Energy Level (n=2) can contain 2 sublevel orbitals Third Energy Level (n=3) can contain 3 sublevel orbitals and so on… There are many types of sublevels:

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Name Shape s p Maximum # of electrons 2 6 Spherical Dumbell Lowest Energy Highest Energy Dumbell

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NameShape d f Maximum # of electrons Lowest Energy Highest Energy f

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What type of sublevel orbital(s) would be found in the first principle energy level (n=1)? How many electrons will it hold? What type of sublevel orbital(s) would be found in the second principle energy level (n=2)? How many electrons will it hold? What type of sublevel orbital(s) would be found in the third principle energy level (n=3)? How many electrons will it hold? The next sublevel is g. How many electrons would it hold?

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1s vs 2s vs 3s orbitals

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Each sublevel orbital can hold 2 electrons, which have opposite magnetic fields. Therefore, we say that each electron has a spin, which is opposite of each other. This is symbolized by: Called the Pauli exclusion principle

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Electron Configurations

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Using quantum numbers to give the arrangement of electrons around the nucleus. Using quantum numbers to give the arrangement of electrons around the nucleus. There are three rules that must be followed! There are three rules that must be followed!

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Rule #1 AUFBAU principle AUFBAU principle Electrons fill low energy orbitals first Electrons fill low energy orbitals first s,p,d then fs,p,d then f Filling orderFilling order 1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p 1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p

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Rule #2 Pauli Exclusion Principle Pauli Exclusion Principle Since there are two possible spins for an electron, no more than two electrons may fill an orbital. Since there are two possible spins for an electron, no more than two electrons may fill an orbital. Remember: s = 1 orbital, p = 3 orbitals, d = 5 orbitals and f = 7 orbitalsRemember: s = 1 orbital, p = 3 orbitals, d = 5 orbitals and f = 7 orbitals

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Rule # 3 Hunds Rule Hunds Rule When multiple shapes are present, electrons fill orbitals with parallel spins before pairing up. When multiple shapes are present, electrons fill orbitals with parallel spins before pairing up. Must follow rule #2!Must follow rule #2! Example 2p Example 2p

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Write the following electron configurations 1. Li 2. Na 3. Be 4. C 5. Si

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Using the Periodic Table 1. Read from left to right and top to bottom. 2. Stop when you: a. Reach the end of a row b. Change color c. Reach the element of interest 3. Try the following Mg, B, Ne and Cl

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Short-Cut Skip back to the previous Noble Gas (core electrons) and start with the element after that. Skip back to the previous Noble Gas (core electrons) and start with the element after that. Try: I, U, Fe Try: I, U, Fe

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