Electron Configuration and Lewis Dot Structures

1. Electron Configuration and Lewis Dot Structures

2. Atomic Orbitals • Energy levels (shells) = n • n = 1, 2, 3….etc. • The higher the energy level, the farther away from the nucleus • Sublevels • Designated by s, p, d, f • Refers to the shape (s) of the area in which the electron can be located • Also designates an energy level within the shell • Represents the region in space where the electron is most likely to be – show 90% probability

3. Atomic Orbitals cont. • Denoted by letters – indicate shape • s orbitals – sphere shaped • Can accommodate 2 electrons • p orbitals – dumbbell shaped • Can accommodate 6 electrons • d orbitals – more complex; flower shaped or double dumbbells • Can accommodate 10 electrons • f orbitals – even more complex • Can accommodate 14 electrons • Relative energy: s < p < d < f

4. s subshell: spherical 1 orbital p subshell: pair of lobes z x y

5. Electron Configurations • Definition: the ways in which electrons are arranged around the nucleus of an atom • Show the approximate location of electrons • Represent in which orbitals electrons are located

6. Electron Configurations cont.Aufbau Principle • Electron configuration determined since electrons tend to be in lowest energy orbitals. • Rules: • The Aufbau principle (“building up”) guides us in the filling of orbitals: • Fill lowest energies first. • Maximum of two electrons with opposite spins in each orbital. (Pauli’s Exclusion Principle) • Degenerate orbitals (orbitals with same energy) follow Hund’s rule

7. Electron Configurations cont.Hund’s Rule • Hund’s rule: If two or more orbitals have the same energy, fill each orbital with one electron before pairing electrons.

8. Periodic Table and Electron Configurations • Build-up order given by position on periodic table; row by row. • Elements in same column will have the same outer shell electron configuration.

9. Electron Configurations cont. • 1st shell has 1 subshell (s) • Holds maximum of 2 electrons energy 1s Helium 1s 1 s2 Hydrogen 1 s1

10. Electron Configuration cont. • Electron Configuration for Li (Z=3) 2p 2s Li 1s 2s 2ndshell 1s Orbital Energy Level Diagram Li 1s22s1 Electronic configuration

11. Electron Configuration cont. • Electron Configuration for Boron (Z = 5) 2p 2s 2p 2s 2ndshell 2ndshell 1s 1s 2p 2s B 1s 2s Be 1s B 1s22s22p1 Be 1s22s2

12. D Subshell x y xy xz yz z2 x2-y2

13. Examples • Fill according to the Energy Level Diagram • Problems • Carbon (C) • Neon (Ne) • Sodium (Na)

14. Electron Dot Diagrams (aka Lewis Dot Structures) • How do we draw a picture for the number of electrons an atom has? • If you want to see how atoms of one element will react, it is handy to have an easier way to represent the atoms and the electrons in their outer energy levels. • You can do this with electron dot diagrams. • An electric dot diagramis the symbol for the element surrounded by as many dots as there are electrons in its outer energy level.

15. How to Write E.D.D.’s • The dots are written in pairs on four sides of the element symbol. • Start by writing one dot on the top of the element symbol, then work your way around adding dots to the right, bottom, and left.

16. How to Write E.D.D.’s • Add a fifth dot to the top to make a pair. Continue in this manner until you reach eight dots to complete the level.