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.

Bohr’s Model Bohr’s atomic model of electrons in orbits with specific levels of energy was only partly correct. The idea of electron shells is not quite sufficient to explain the behaviour of atoms. We need to add the concept of orbitals and quantum numbers for elements with multiple electrons. http://www.th.physik.uni-frankfurt.de/~jr/gif/phys/nbohr.jpg

Orbitals In Bohr’s model, electrons existed within main energy levels Now  electrons still exist in main energy levels BUT within each level there are sublevels called orbitals.

Principal Quantum Number, n The principal quantum number represents the shell or main energy level. Main energy levels are given values: n = 1, 2, 3, 4… The shell or main energy level indicates the the size of an orbital (or how far away the electron is from the nucleus)  the higher the number, the larger the orbital (or the farther the electron). As n increases, so does energy.

Principal Quantum Number describes the size!! Relative Sizes 1s and 2s Principal Quantum Number describes the size!! 1s 2s Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 334

Secondary Quantum Number, l The secondary quantum number divides the shells or main energy levels up into smaller groups of subshells called orbitals it also describes the shape of orbital.

Secondary Quantum Number, l Subshells are given letter codes: s, p, d, f, g… There is one s-shaped orbital within each main energy level. There are three p-shaped orbitals within main energy levels 2+. Each of the p-shaped orbitals have a different orientation in space.

There are five d-shaped orbitals within main energy levels 3+ There are five d-shaped orbitals within main energy levels 3+. Each of the d-shaped orbitals have a different orientation in space. There are seven f-shaped orbitals within main energy levels 4+. Each of the f-shaped orbitals have a different orientation in space.

Secondary Quantum Number, l Within a given shell, the subshells (orbitals) are in order of increasing energy: 4s < 4p < 4d < 4f (increasing energy)

Magnetic Quantum Number, ml Splits the subshells into individual orbitals. Describes orientation in space, thus gives 3D information.

Maximum Number of Electrons In Each Sublevel Sublevel Number of Orbitals of Electrons s 1 2 p 3 6 d 5 10 f 7 14 LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 146

Shapes of s, p, and d-Orbitals http://www.unit5.org/christjs/site%20map.htm

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

Spin Magnetic Number, ms Indicates the orientation of the two electrons in each orbital. Values are +1/2 or –1/2

- Spin Quantum Number, ms North South S N The electron behaves as if it were spinning about an axis through its center. This electron spin generates a magnetic field, the direction of which depends on the direction of the spin. Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 208

Atomic Orbitals http://www.unit5.org/christjs/site%20map.htm

Principal Energy Levels 1 and 2 http://www.unit5.org/christjs/site%20map.htm

s, p, and d-orbitals Kelter, Carr, Scott, , Chemistry: A World of Choices 1999, page 82

Electron Configurations Objectives: To state the energy sublevels within a given energy level. To state the maximum number of electrons that occupy a given energy level and sublevel. To list the order of sublevels according to increasing energy. To write the predicted electron configurations for selected elements.

How do we fill orbitals? Atom is most stable when electrons have the lowest possible energy. That is when they occupy the lowest possible energy orbitals available.

Filling Rules for Electron Orbitals Aufbau Principle: Electrons are added one at a time to the lowest energy orbitals available until all the electrons of the atom have been accounted for. Pauli Exclusion Principle: An orbital can hold a maximum of two electrons. To occupy the same orbital, two electrons must spin in opposite directions. NO TWO ELECTRONS CAN HAVE THE SAME FOUR QUANTUM NUMBERS!! Hund’s Rule:Within a given set of orbitals, one electron will go in each orbital before pairing-up begins.

Energy Level Diagram of a Many-Electron Atom 6s 6p 5d 4f 32 5s 5p 4d 18 4s 4p 3d Arbitrary Energy Scale 18 3s 3p 8 2s 2p 8 1s 2 NUCLEUS O’Connor, Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 177

Sublevels 4f 4d 4p 4s n = 4 3d 3p 3s n = 3 Energy 2p 2s n = 2 1s n = 1 http://www.unit5.org/christjs/site%20map.htm

Electron Configurations and the Periodic Table http://www.unit5.org/christjs/site%20map.htm Electron Configurations and the Periodic Table

H He Li C N Al Ar F Fe La Energy Level Diagram Bohr Model http://www.unit5.org/christjs/site%20map.htm 6s 6p 5d 4f Bohr Model 5s 5p 4d 4s 4p 3d Arbitrary Energy Scale 3s 3p N 2s 2p 1s Electron Configuration NUCLEUS H He Li C N Al Ar F Fe La CLICK ON ELEMENT TO FILL IN CHARTS

Hydrogen H = 1s1 H He Li C N Al Ar F Fe La Energy Level Diagram http://www.unit5.org/christjs/site%20map.htm Hydrogen 6s 6p 5d 4f Bohr Model 5s 5p 4d 4s 4p 3d Arbitrary Energy Scale 3s 3p N 2s 2p 1s Electron Configuration NUCLEUS H = 1s1 H He Li C N Al Ar F Fe La CLICK ON ELEMENT TO FILL IN CHARTS

Helium He = 1s2 H He Li C N Al Ar F Fe La Energy Level Diagram http://www.unit5.org/christjs/site%20map.htm Helium 6s 6p 5d 4f Bohr Model 5s 5p 4d 4s 4p 3d Arbitrary Energy Scale 3s 3p N 2s 2p 1s Electron Configuration NUCLEUS He = 1s2 H He Li C N Al Ar F Fe La CLICK ON ELEMENT TO FILL IN CHARTS

Lithium Li = 1s22s1 H He Li C N Al Ar F Fe La Energy Level Diagram http://www.unit5.org/christjs/site%20map.htm Lithium 6s 6p 5d 4f Bohr Model 5s 5p 4d 4s 4p 3d Arbitrary Energy Scale 3s 3p N 2s 2p 1s Electron Configuration NUCLEUS Li = 1s22s1 H He Li C N Al Ar F Fe La CLICK ON ELEMENT TO FILL IN CHARTS

Carbon C = 1s22s22p2 H He Li C N Al Ar F Fe La Energy Level Diagram http://www.unit5.org/christjs/site%20map.htm Carbon 6s 6p 5d 4f Bohr Model 5s 5p 4d 4s 4p 3d Arbitrary Energy Scale 3s 3p N 2s 2p 1s Electron Configuration NUCLEUS C = 1s22s22p2 H He Li C N Al Ar F Fe La CLICK ON ELEMENT TO FILL IN CHARTS

Nitrogen N = 1s22s22p3 H He Li C N Al Ar F Fe La Energy Level Diagram http://www.unit5.org/christjs/site%20map.htm Nitrogen 6s 6p 5d 4f Bohr Model 5s 5p 4d 4s 4p 3d Arbitrary Energy Scale 3s 3p N Hund’s Rule “maximum number of unpaired orbitals”. 2s 2p 1s Electron Configuration NUCLEUS N = 1s22s22p3 H He Li C N Al Ar F Fe La CLICK ON ELEMENT TO FILL IN CHARTS

Electron Configurations http://www.unit5.org/christjs/site%20map.htm Electron Configurations Orbital Filling Element 1s 2s 2px 2py 2pz 3s Configuration Electron H He Li C N O F Ne Na 1s1 1s2 1s22s1 1s22s22p2 1s22s22p3 1s22s22p4 1s22s22p5 1s22s22p6 1s22s22p63s1