1. Electron Configurations!

2. Electron configurations describe where the electrons are in a given atom. e- are arranged in up to 7 energy levels Lower E levels fill up first (Aufbrau principle) E levels have 4 orbitals: s,p,d,f 2 electrons per orbital (Pauli)

3. Hydrogen, for example, has one electron in a spherical s orbital. There is a high probability that the electron is somewhere in this “cloud”, a certain radius from the nucleus.

4. Therefore, the electron configuration for hydrogen is: 1S 1 The S denotes the electron is in the S orbital. 1 denotes the electron is in period 1. Superscript 1 denotes there is 1 electron in the 1S orbital.

5. The electron configuration for helium is 1S 2 Meaning, there are 2 electrons in the 1S enegy level of helium! Lithium has 3 electrons However an S orbital can only hold a maximum of 2 electrons Therefore Li has 2 1S electrons and 1 2S electron 1S 2 2S 1

6. Beryllium is 1S 2 2S 2 Since S orbitals can only hold 2 electrons, the 5 th electron, found in boron creates a new orbital, called a “p”.

7. Our next element boron, B has one more electron than Be. Since S orbitals can hold a maximum of 2, the new electron creates a new “p” orbital. This is balloon shaped and the orbitals exist in pairs along 3 axes, x, y and z in the second shell.

8. Boron is 1S 2 2S 2 2p 1 As each atom adds another electron, into the p orbital, the electron # goes to 2, 3. 4. 5. and 6 with Ne. Therefore C is 1S 2 2S 2 2p 2 Ne is 1S 2 2S 2 2p 6 Notice the first number is the shell the letter is the orbital shape the superscript is the number of e- Notice how different this looks compared to prior models:

9. D orbitals are different than s or p:

10. When we get to the d suborbital, d electrons have lower energy than s or p electrons Therefore Sc has a 3d electron. The d electron is in the third energy level: 1S 2 2S 2 2p 6 3s 2 3p 6 4S 2 3d 1

11. The Periodic Table has s, p, d, f blocks:…

12. Notice the s, p, d, f electron configs for valence e-

13. Shortcuts: You can write a shortcut to the electron configuration by going back to the last noble gas, putting it in brackets, and then adding the outer shell. Example: Mg, 1S 2 2S 2 2p 6 3s 2 becomes [Ne]3s 2

14. Question: Knowing electron configurations: Hot or Not?

15. Definitely HOT!

16. The End