1. Chemistry Ch. 5 Notes #2
Electrons in Atoms

2. Energy of Atoms Energy Levels Where electrons are found
Principal Energy Levels (p.e.l.)
7 “orbits” – each has one or more sublevels in it
The number of sublevels in any p.e.l. is the same as its number “n”.
Ex. P.e.l. 1 has 1……. p.e.l. 2 has 2, etc
p.e.l’s are represented by numbers 1-7

3. Energy of Atoms Sublevels Designated by numbers and letters
The # represents the p.e.l
The letter refers to the sublevel
First 4 sublevels = s, p, d, f
Each electron has specific energy
Each p.e.l. has as many sublevels as its number “n”
Energy level 1 = 1 sublevel = 1s
Energy level 2 = 2 sublevels = 2s and 2p
Energy level 3 = 3 sublevels = 3s, 3p, and 3d

4. Energy of Atoms Principal energy level Sublevels 1 1s 2 2s 2p 3
3s p d 4
4s p d f 5
5s p d f 6
6s p d f

5. Shapes of Sublevels All s orbitals are spherical.
Each new p.e.l. s sublevel is bigger than the last
2s is larger than 1s

6. Shapes of Sublevels All p orbitals are dumb-bell shaped
px, pz, and py each have a different orientation

7. Energy of Atoms
The d and f sublevels do not all have the same shapes…..
Inside the sublevels = orbitals
Each orbital holds 2 electrons
The 2 electrons have opposite “spins”
Compared to earth’s rotation on its axis
With each new sublevel there are 2 more orbitals available

8. Energy of Atoms p.e.l # orbitals Max # of e- 2n2 n s p d f 1 - 2 3 4 8
Number of Orbitals Available
# orbitals n2
Max # of e-
2n2 n s p d f 1 - 2 3 4 8 5 9 18 7 16 32

9. Sublevels Orbitals are drawn out as boxes
The 3 p orbitals are referenced as px, py, pz
Each orbital holds 2 electrons
In Mult. Orbital sublevels, each orbital has to have 1 e- of the same spin before they double up (by gaining a second e- of the opposite spin)

10. Sublevels
Electrons always fill from lowest energy levels to highest energy levels
No electron can remain in a particular orbital if there is a vacant orbital at lower energy
Once you get to the 3rd p.e.l. there is overlap in energy amongst the levels
If an electron jumps to a higher level (an “excited” state) it emits frequencies of light (emission spectra) to go back to “ground state”

11. Sublevels

12. Electron Configurations
The arrangement of electrons among the various orbitals of an atom is called the electron configuration
It is written using a notation that tells us the p.e.l. and sublevels that are filled.
Every element has a different electron configuration

13. Electron Configurations
Order that sublevels fill….
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

14. Electron Configurations
Element
Atomic #
Orbital Diagram
Electron Configuration H 1 He 2 Li 3 Be 4

15. Electron Configurations
Element
Atomic #
Orbital Diagram
Electron Configuration B 5 C 6 N 7 O 8 F 9 Ne 10 Na 11 Mg 12