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Slide 2 1 Chapter 13 Electrons in the atom Slide 3 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 Slide 4 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) Slide 5 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 Slide 6 5 Slide 7 6 Slide 8 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. Slide 9 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 Slide 10 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. Slide 11 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? Slide 12 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. Slide 13 Slide 14 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. Slide 15 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 Slide 16 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 = Plancks constant = h = Plancks 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 Slide 17 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. Slide 18 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 Slide 19 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. Slide 20 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 Slide 21 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 Slide 22 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 Slide 23 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) Slide 24 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 Slide 25 24 The next pictures are from Zumdahl, Chemistry, 3rd. ed.) The next pictures are from Zumdahl, Chemistry, 3rd. ed.) Slide 26 25 p. 154 also Slide 27 26 Slide 28 27 Slide 29 28 Slide 30 29 Slide 31 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 Slide 32 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 Slide 33 32 sublevels Number of orbitals 1s 5p 4d 4f 7s 3p 5d 1 3 5 7 1 3 5 Slide 34 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 ) Slide 35 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 ) Slide 36 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 ) Slide 37 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 ) Slide 38 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) Slide 39 More on orbitals and electron configuration | Khan Academy Slide 40 39 Intro to Aufbau Slide 41 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 Slide 42 41 Aufbau Principle Electrons enter the lowest energy levels first. Electrons enter the lowest energy levels first. Slide 43 42 Pauli Exclusion Principle An orbital can hold only 2 electrons with opposite spins. An orbital can hold only 2 electrons with opposite spins. Slide 44 43 Hunds 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. Slide 45 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 Slide 46 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. Slide 47 Valence electrons Electrons in the highest occupied energy level of an elements atoms. Electrons in the highest occupied energy level of an elements 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 Slide 48 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 Slide 49 Electron dot structures (add to WS 8&9) Mg- Mg- N- N- S- S- 48