Electron configurations

1. Electron configurations According to the Wave – Mechanical Model

2. Definition • Shows the arrangement of electrons in the atom

3. Sublevels of PELS • within an energy level, orbitals with different shapes occupy different regions, known as sublevels • the # of the principal energy level will identify the possible number of sublevels • first 4 assigned are the s, p, d, and f

4. S - sublevel • s sublevels have the lowest energy • contains one orbital • each orbital can hold a max of 2 e- • has spherical shape

5. P sublevels • contains 3 orbitals • Max of 6 e-, along 3 axis • has peanut shape

6. D Sublevel • contains 5 orbitals • has double peanut shape

7. F sublevel • contain 7 orbitals • Has most energy of all sublevels

8. Chart of PELs and sublevels

9. The Rules for Electron Configurations • Aufbau principle – an electron occupies the lowest energy orbital that can receive it Fill order: 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f

10. The Aufbau principle helps us to determine the electron configuration of atoms. • Write the electron configuration of an atom of Beryllium (Be) 1. Identify the number of electrons in the atom. Ex) ________

11. 2. Begin to place electrons in the sublevels, by writing the number of electrons that will fit in each sublevel for that atom. Ex) _____________________ 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f

12. Subtract the number of electrons that have been placed in the sublevel from the total number of electrons in the atom (this will tell you how many electrons you have leftover). Continue placing electrons in sublevels, following the fill order, until you run out of electrons for that atom. Ex) _____________________

13. Configurations and the Periodic Table

14. Orbital Notation • graphically represents the arrangement of electrons in their energy levels & sublevels • Hund’s rule : electrons occupying the same orbital must have opposite spins (we’ll show that with arrows), and electrons will fill one electron per orbital (with identical spin) in a sublevel before they double up.

15. Write the electron configuration for N. 1s22s22p3 2p ______ ______ ______ Increasing 2s ______ Energy 1s ______

16. Write the electron configuration for Ne 1s22s22p6 2p ______ ______ ______ Increasing 2s ______ Energy 1s ______

17. Write the electron configuration for O 1s22s22p4 2p ______ ______ ______ Increasing 2s ______ Energy 1s ______

18. Write the electron configuration for Ti 1s22s22p63s23p64s23d2 3d ______ ______ ______ ______ ______ 4s ______ 3p ______ ______ ______ 3s ______ 2p ______ ______ ______ 2s ______ 1s ______

19. Valence Electrons Definition: electrons that occupy the outermost PEL of an atom • Maximum number of valence electrons is 8 Reason: result of full s and p sublevels - energy levels (clouds) begin to overlap from the 3rd to the 4th energy level

20. How many valence electrons are there in the following: Sodium: ________ Argon: ________ Oxygen: ________ Magnesium: ______ Carbon: ________ Strontium: ______

21. Ions Definition: Electrically charged atoms (unequal # of protons and electrons) - formed when atoms lose or gain electrons - in order to have a complete valence energy level (stable configuration) - Possible charges are listed on the Periodic Table

22. Cations Def: a positively charged ion - Formed when atoms lose electrons Ex) Sodium atom Sodium ion (Na+1) Sodium ion configuration same as Neon

23. Anions Def: negatively charged ions • Formed when atoms gain electrons Ex) Fluorine atom Fluoride ion (F-1) Fluoride ion configuration same as Neon