Electron Configuration

1. Electron Configuration Filling of atomic orbital's and energy levels

2. Electron Configuration • A form of notation which shows how the electrons are distributed among the various atomic orbital and energy levels.  • The format consists of a series of numbers, letters and superscripts as shown below He 1s2

3. Information Provided by Electron Configuration - Example He - 1s2 • The large number "1“ in the example, stands for the energy level (refers to the principle quantum number "n" ).  • It tells us that the electrons of helium occupy the first energy level of the atom. • The letter "s” tells us that the electrons of the helium element occupy an "s" or spherical orbital • The exponent "2“ in the example, refers to the total number of electrons in that orbital or sub-shell.  • There are two electrons in the spherical orbital at the first energy level.

4. Information Needed to Understand Electron Configurations! • The number of sublevels that an energy level can contain is equal to the principle quantum number of that level (n).  • For example, the second energy level has two sublevels • The third energy level has three sublevels.  • Names of Sublevels • The first sublevel is called an s sublevel.  f • The second sublevel is called a p sublevel.  d • The third sublevel is called a d sublevel p • The fourth sublevel is called an f sublevel.  S

5. Check Your Progress! • How many sublevels are in the first energy level? • How many sublevels are in the fourth energy level? • What energy level has 3 sublevels? • What energy level has 2 sublevels?

6. Answers • One • Four • Third energy level • The second energy level

7. Sublevels and Orbitals • An orbital is a space that can be occupied by up to two electrons.  • Each type of sublevel holds a different number of orbitals, and therefore, a different number of electrons.  • s sublevels have 1 orbital, which can hold up to two electrons.  • p sublevels have 3 orbitals, each of which can hold 2 electrons, for a total of 6 electrons.  • d sublevels have 5 orbitals, for a possible total of 10 electrons.  • f sublevels, with 7 orbitals, can hold up to 14 electrons. 

8. Electron Capacity of Sublevels

9. Total Number of Orbital and Electrons per Energy Level • An easy way to calculate the number of orbitals found in an energy level is to use the formula n2.  (n=the energy level) • For example, the third energy level (n=3) has a total of 32, or nine orbitals.  • This makes sense because we know that the third energy level would have 3 sublevels; • an s sublevel with 1 orbital, a p sublevel with 3 orbitals and a d sublevel with 5 orbitals.  1 + 3 + 5 = 9, so the formula n2 works!

10. Lets check your progress again! • How many orbitals are found in the fourth energy level? • Which sublevels will it have? • How many orbitals are in each of the sublevels?

11. Answers • n=4 • N2 , 42 or 16 orbitals! • an s sublevel with one orbital • a p sublevel with 3 orbitals • a d sublevel with 5 orbitals. • An f sublevel with 7 orbitals

12. Total Number of Electrons per Energy Level • An easy way to calculate the total number of electrons that can be held by a given energy level is to use the formula 2n2.   • For example, the fourth energy level (n=4) can hold 2(4)2 = 32 electrons.  • This makes sense because the fourth energy level would have four sublevels, one of each of the named types.  • The s sublevel hold 2 electrons, • the p sublevel holds 6 electrons , • the d sublevel holds 10 electrons and the f sublevel holds 14 electrons.  • 2 + 6 + 10 + 14 = 32, so the formula 2n2 works! 

13. Lets check your progress • How many electrons can the third energy level hold? • How do you know?

14. Answer • the third energy level (n=3) can hold 2(3)2 = 18 electrons.  • This makes sense because the third energy level would have three sublevels, one of each of the named types.  • The s sublevel hold 2 electrons, • the p sublevel holds 6 electrons , • the d sublevel holds 10 electrons • 2 + 6 + 10 = 18, so the formula 2n2 works! 

15. Electron Capacity of the First 4 Energy Levels

16. Different Shapes of Orbitals

17. Order of Filling Sublevels with Electrons • The energy sublevels are filled in a specific order • You must follow the rules to understand when electrons will fill each level • Once you know this you can write them out in electron configuration

18. Start at the beginning of each arrowthen follow it all of the way to the end, filling in the sublevels that it passes through

19. Check up from the neck up! • What is the order in which sublevels are filled by electrons? • Please write it out through the seventh energy level! • Hint!!!! --- draw the diagram first then use it!

20. Look carefully at the order! • the order for filling in the sublevels becomes; 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d,7p.

21. Remember! • How many electrons do each of these energy levels hold? • S holds 2 • P holds 6 • D holds 10 • F holds 14

23. Write electron configurations for each of these elements • K • Ag • C

24. Answer • K has 19 electrons- 1s22s22p63s23p64s1 • (S holds 2, P holds 6) • Ag has 47 electrons- 1s22s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d10 (to make it neater we write the energy levels together like this- 1s2 2s2p6 3s2p6d10 4s2p6d105s1 ) 3 C has 6 electrons- 1s2 2s2 2p2