Electron Configuration & Orbitals Quantum Model of the Atom Ch. 4 - Electrons in Atoms Electron Configuration & Orbitals 1s22s22p63s23p64s23d104p65s24d104p65s24d105p66s24f145d106p6… Objectives: To describe the quantum mechanical model of the atom. To describe the relative sizes and shapes of s and p orbitals.

Quantum Model of the Atom Ch. 4 - Electrons in Atoms Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Electrons as Waves Louis de Broglie (1924) Applied wave-particle theory to electrons electrons exhibit wave properties Louis de Broglie ~1924 QUANTIZED WAVELENGTHS Fundamental mode Second Harmonic or First Overtone Standing Wave 200 150 100 50 - 50 -100 -150 -200 200 150 100 50 - 50 -100 -150 -200 200 150 100 50 - 50 -100 -150 -200 0 50 100 150 200 0 50 100 150 200 0 50 100 150 200 Adapted from work by Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Electrons as Waves QUANTIZED WAVELENGTHS Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Electrons as Waves Evidence: DIFFRACTION PATTERNS VISIBLE LIGHT Davis, Frey, Sarquis, Sarquis, Modern Chemistry 2006, page 105 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Quantum Mechanics Heisenberg Uncertainty Principle Impossible to know both the velocity and position of an electron at the same time Werner Heisenberg ~1926 g Microscope Werner Heisenberg (1901 - 1976) The uncertainty principle: a free electron moves into the focus of a hypothetical microscope and is struck by a photon of light; the photon transfers momentum to the electron. The reflected photon is seen in the microscope, but the electron has moved out of focus. The electron is not where it appears to be. Electron

Quantum Mechanics Schrödinger Wave Equation (1926) finite # of solutions  quantized energy levels defines probability of finding an electron Erwin Schrodinger ~1926 Erwin Schrodinger (1887 - 1926) won the Nobel Prize in Physics in 1933. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Quantum Mechanics Orbital (“electron cloud”) Region in space where there is 90% probability of finding an electron 90% probability of finding the electron Orbital Electron Probability vs. Distance 40 30 Electron Probability (%) 20 10 50 100 150 200 250 Distance from the Nucleus (pm) Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Quantum Numbers Four Quantum Numbers: Specify the “address” of each electron in an atom UPPER LEVEL Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Quantum Numbers Principal Quantum Number ( n ) Angular Momentum Quantum # ( l ) Magnetic Quantum Number ( ml ) Spin Quantum Number ( ms )

Relative Sizes 1s and 2s 1s 2s Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 334

Quantum Numbers 1. Principal Quantum Number ( n ) Energy level Size of the orbital n2 = # of orbitals in the energy level 1s 2s 3s Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Quantum Numbers y y y z z z x x x px pz py

p-Orbitals px pz py Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 335

Quantum Numbers f d s p 2. Angular Momentum Quantum # ( l ) Energy sublevel Shape of the orbital f d s p Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Quantum Numbers 2s 2px 2py 2pz Orbitals combine to form a spherical shape. 2s 2pz 2py 2px Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Quantum Numbers n = # of sublevels per level Principal level n = 1 n = 2 n = 3 Sublevel s s p s p d Orbital px py pz px py pz dxy dxz dyz dz2 dx2- y2 n = # of sublevels per level n2 = # of orbitals per level Sublevel sets: 1 s, 3 p, 5 d, 7 f Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Maximum Capacities of Subshells and Principal Shells n 1 2 3 4 ...n l 0 0 1 0 1 2 0 1 2 3 Subshell designation s s p s p d s p d f Orbitals in subshell 1 1 3 1 3 5 1 3 5 7 Subshell capacity 2 2 6 2 6 10 2 6 10 14 Principal shell capacity 2 8 18 32 ...2n2 Hill, Petrucci, General Chemistry An Integrated Approach 1999, page 320

Quantum Numbers 3. Magnetic Quantum Number ( ml ) Orientation of orbital Specifies the exact orbital within each sublevel Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

d-orbitals Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 336

Shapes of s, p, and d-Orbitals

Atomic Orbitals

s, p, and d-orbitals A s orbitals: Hold 2 electrons (outer orbitals of Groups 1 and 2) B p orbitals: Each of 3 pairs of lobes holds 2 electrons = 6 electrons (outer orbitals of Groups 13 to 18) C d orbitals: Each of 5 sets of lobes holds 2 electrons = 10 electrons (found in elements with atomic no. of 21 and higher) Kelter, Carr, Scott, , Chemistry: A World of Choices 1999, page 82

Principal Energy Levels 1 and 2

Quantum Numbers 4. Spin Quantum Number ( ms ) Electron spin  +½ or -½ An orbital can hold 2 electrons that spin in opposite directions. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Quantum Numbers Pauli Exclusion Principle No two electrons in an atom can have the same 4 quantum numbers. Each electron has a unique “address”: 1. Principal #  2. Ang. Mom. #  3. Magnetic #  4. Spin #  energy level sublevel (s,p,d,f) orbital electron Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Feeling overwhelmed? Read Section 4-2! Chemistry "Teacher, may I be excused? My brain is full." Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

(a) 1s orbital (b) 2s and 2p orbitals Electron Orbitals: Electron orbitals Equivalent Electron shells (a) 1s orbital (b) 2s and 2p orbitals c) Neon Ne-10: 1s, 2s and 2p 1999, Addison, Wesley, Longman, Inc.

What sort of covalent bonds are seen here? O O (a) H2 (b) O2 H O C H H O O H (c) H2O (d) CH4