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1 Chapter 13 Electrons in the atom

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2 Atomic Theory Dalton Dalton Atom – What would his atom look like? Atom – What would his atom look like? Rutherford Rutherford Atom – mostly empty space Atom – mostly empty space Nucleus with protons and neutrons Nucleus with protons and neutrons Electrons outside of nucleus Electrons outside of nucleus Thomson Thomson Electron – Choc. Chip Ice Cream Electron – Choc. Chip Ice Cream

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3 Nucleus What charge does the nucleus have? What charge does the nucleus have? What keeps the protons in the nucleus together? What keeps the protons in the nucleus together? Neutrons (discovered later) Neutrons (discovered later) Strong force (theory came later) Strong force (theory came later)

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4 Niels Bohr Where are the electrons? Where are the electrons? What keeps them from spiraling into the nucleus? What keeps them from spiraling into the nucleus? Proposed – planetary explanation Proposed – planetary explanation

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7 Energy Levels Region of space around the nucleus where the electron is most likely moving. (3-D) Region of space around the nucleus where the electron is most likely moving. (3-D) Electrons located on specific energy levels surrounding the nucleus. Electrons located on specific energy levels surrounding the nucleus.

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8 Energy Levels Electrons located on specific energy levels surrounding the nucleus. Electrons located on specific energy levels surrounding the nucleus. Electrons have fixed energy that keeps them from falling into the nucleus. Electrons have fixed energy that keeps them from falling into the nucleus. Similar to rungs on a ladder Similar to rungs on a ladder

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9 Energy levels To move from one energy level to another, an electron has to have specific amount of energy (quantum). To move from one energy level to another, an electron has to have specific amount of energy (quantum). Energy levels not equally spaced. Energy levels not equally spaced. Energy levels more closely spaced the farther away from the nucleus. Energy levels more closely spaced the farther away from the nucleus.

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10 Energy levels Higher energy levels have more energy. Higher energy levels have more energy. Farther away from the nucleus, the easier it is for an electron to “escape” from an atom. Farther away from the nucleus, the easier it is for an electron to “escape” from an atom. Why? Why?

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11 Quantum Quantum is a specific amount of energy needed to move an electron from one level to another level. Quantum is a specific amount of energy needed to move an electron from one level to another level. Has to be that exact amount of energy for the electron to change levels. Has to be that exact amount of energy for the electron to change levels.

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The Wave-like Electron Louis deBroglie The electron propagates through space as an energy wave. To understand the atom, one must understand the behavior of electromagnetic waves.

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14 Given that light behaves as waves and particles, can particles of matter behave as waves? Birth of quantum mechanics Birth of quantum mechanics deBroglie derived an equation that described the wavelength of a moving particle. deBroglie derived an equation that described the wavelength of a moving particle. = h /mv = h /mv Mass = mass of particle Mass = mass of particle v = velocity of particle v = velocity of particle

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15 Wavelength of an electron Mass = 9.11 x 10 -28 g Mass = 9.11 x 10 -28 g Speed = 3.00 x 10 10 cm / sec Speed = 3.00 x 10 10 cm / sec h = Planck’s constant = h = Planck’s constant = h = 6.6262 x 10 -34 J x s h = 6.6262 x 10 -34 J x s = wavelength of electron = 2.42 x 10 -15 m = wavelength of electron = 2.42 x 10 -15 m

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16 Heisenberg uncertainty principle It is impossible to know exactly both the velocity and the position of a particle at the same time. It is impossible to know exactly both the velocity and the position of a particle at the same time.

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17 Quantum Mechanical Theory Erwin Schrodinger -1926 physicist Erwin Schrodinger -1926 physicist Used a mathematical equation to describe the location and energy of an electron. Used a mathematical equation to describe the location and energy of an electron. New theory!! New theory!! No models to really describe the location, movement and energy of electron. No models to really describe the location, movement and energy of electron. Best one is bees around a beehive Best one is bees around a beehive

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18 Quantum Mechanical Model Definition: Describes the probability of finding an electron in a certain region. Definition: Describes the probability of finding an electron in a certain region. Best description of the electrons in an atom. Best description of the electrons in an atom.

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19 Movement of electron Does not move in a set path! (contrary to Bohr) Does not move in a set path! (contrary to Bohr) Atom mostly empty space Atom mostly empty space High speed – illusion of a solid High speed – illusion of a solid Based on probability Based on probability

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20 Electron Probability Clouds Shape of space where the electrons will be located 90% of the time. Shape of space where the electrons will be located 90% of the time. In Quantum Mechanical Model – these are called Atomic Orbitals In Quantum Mechanical Model – these are called Atomic Orbitals

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21 Quantum Mechanical Model Energy levels = n Energy levels = n Principal quantum number Principal quantum number n = 1,2,3,4,5 …… (check out side of the Periodic Table) n = 1,2,3,4,5 …… (check out side of the Periodic Table) Higher the number the farther away from nucleus. Higher the number the farther away from nucleus. Higher the number the greater the energy Higher the number the greater the energy

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22 Energy sublevels Each energy level has sublevels Each energy level has sublevels The number of sublevels = the principal quantum number The number of sublevels = the principal quantum number Level 1 has 1 sublevel (s) Level 1 has 1 sublevel (s) Level 2 has 2 sublevels (s,p) Level 2 has 2 sublevels (s,p) Level 3 has 3 sublevels (s,p,d) Level 3 has 3 sublevels (s,p,d)

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23 Electron Probability Clouds (p. 154) Shapes of Atomic Orbitals Shapes of Atomic Orbitals s= spherical s= spherical p = dumbbell p = dumbbell d = 4-leaf clover, dumbbell w/ ring d = 4-leaf clover, dumbbell w/ ring f = very complex f = very complex At the nodes (near nucleus) - probability = 0 of finding an electron At the nodes (near nucleus) - probability = 0 of finding an electron

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24 The next pictures are from Zumdahl, Chemistry, 3rd. ed.) The next pictures are from Zumdahl, Chemistry, 3rd. ed.)

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25 p. 154 also

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30 Principal energy level Number of sublevels Type of sublevel n=1 n=11 s n=2 n=22 s,p s,p n=3 n=33 s,p,d s,p,d n =4 n =44 s,p,d,f s,p,d,f

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31 Atomic orbitals Regions around the nucleus - probability of locating the electrons (s, p, d, f) Regions around the nucleus - probability of locating the electrons (s, p, d, f) s have 1 orbital s have 1 orbital p have 3 orbitals p have 3 orbitals d have 5 orbitals d have 5 orbitals f have 7 orbitals f have 7 orbitals

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32 sublevels Number of orbitals 1s 5p 4d 4f 7s 3p 5d 1 3 5 7 1 3 5

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33 Principal Energy levels n =1 n =1 1 sublevel; s 1 sublevel; s 1s (1 orbital) 1s (1 orbital) Number of orbitals (n 2 ) = 1 Up to 2 electrons in each orbital Total of 2 electrons (2n 2 ) Total of 2 electrons (2n 2 )

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34 Principal Energy levels n =2 n =2 2 sublevel; s and p 2 sublevel; s and p 2s (1 orbital) 2s (1 orbital) 2p (3 orbitals) 2p (3 orbitals) Number of orbitals (n 2 ) = 4 Up to 2 electrons in each orbital Up to 2 electrons in each orbital Total of 8 electrons (2n 2 ) Total of 8 electrons (2n 2 )

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35 Principal Energy levels n = 3 n = 3 3 sublevel; s p d 3 sublevel; s p d 3s (1 orbital) 3s (1 orbital) 3p (3 orbitals) 3p (3 orbitals) 3d (5 orbitals) 3d (5 orbitals) Number of orbitals (n 2 = 9) Number of orbitals (n 2 = 9) Up to 2 electrons in each orbital Up to 2 electrons in each orbital Total of 18 electrons (2n 2 ) Total of 18 electrons (2n 2 )

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36 Principal Energy levels n = 4 n = 4 4 sublevel; s p d f 4 sublevel; s p d f 4s (1 orbital) 4s (1 orbital) 4p (3 orbitals) 4p (3 orbitals) 4d (5 orbitals) 4d (5 orbitals) 4f (7 orbitals) 4f (7 orbitals) Number of orbitals (n 2 = 16) Number of orbitals (n 2 = 16) Up to 2 electrons in each orbital Up to 2 electrons in each orbital Total of 32 electrons (2n 2 ) Total of 32 electrons (2n 2 )

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37 Energy level Type of sublevel s Number of orbitals Maximum # of electrons n=1 n=1 s12 n=2 n=2 s,p s,p48 n=3 n=3 s,p,d s,p,d918 n=4 n=4 s,p,d,f s,p,d,f1632 (Relate to Bohr model from 9 th grade)

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More on orbitals and electron configuration | Khan Academy

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39 Intro to Aufbau

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Orbitals and the Periodic Table Orbitals grouped in s, p, d, and f orbitals Orbitals grouped in s, p, d, and f orbitals s orbitals p orbitals d orbitals f orbitals

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41 Aufbau Principle Electrons enter the lowest energy levels first. Electrons enter the lowest energy levels first.

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42 Pauli Exclusion Principle An orbital can hold only 2 electrons with opposite spins. An orbital can hold only 2 electrons with opposite spins.

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43 Hund’s Rule When electrons occupy orbitals of the same energy (ex: p, d or f), one electron enters each orbital with parallel spins. When electrons occupy orbitals of the same energy (ex: p, d or f), one electron enters each orbital with parallel spins.

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Diagonal Rule The diagonal rule is a memory device that helps you remember the order of the filling of the orbitals from lowest energy to highest energy _____________________ states that electrons fill from the lowest possible energy to the highest energy

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Diagonal Rules s 3p 3d s 2p s 4p 4d 4f s 5p 5d 5f 5g? s 6p 6d 6f 6g? 6h? s 7p 7d 7f 7g? 7h? 7i? 1234567 Steps: 1.Write the energy levels top to bottom. 2.Write the orbitals in s, p, d, f order. Write the same number of orbitals as the energy level. 3.Draw diagonal lines from the top right to the bottom left. 4.To get the correct order, follow the arrows! By this point, we are past the current periodic table so we can stop.

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Valence electrons Electrons in the highest occupied energy level of an element’s atoms. Electrons in the highest occupied energy level of an element’s atoms. Usually s and or p Usually s and or p Determines the chemical properties of an element. Determines the chemical properties of an element. Usually the only electrons used in a chemical reaction forming new bonds Usually the only electrons used in a chemical reaction forming new bonds *shortcut* *shortcut* # determined by “A” group number # determined by “A” group number

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Valence electrons Related to the group number in the periodic table Related to the group number in the periodic table Group 1A = 1 valence electrons Group 1A = 1 valence electrons Group 2A = 2 valence electrons Group 2A = 2 valence electrons Group 8A = 8 valence electrons Group 8A = 8 valence electrons

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Electron dot structures (add to WS 8&9) Mg- Mg- N- N- S- S- 48

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