Electron Configurations Unit 3

What are electron configurations? According to the wave mechanical model, the electrons in an atom move around in the orbitals surrounding the nucleus. There are 7 orbitals!  They are numbered 1 – 7!  Each orbital has sublevels!

Sublevels! They are labeled s, p, d, and f!  Each sublevel has a different shape to it!

s - sublevel

p Sublevel

d - sublevels

f - sublevels

Each sublevel has a certain # of “rooms” that 2 electrons reside in. s has 1 “room” p has 3 “rooms” d has 5 “rooms” f has 7 “rooms” How many electrons fit in each sublevel total?

Electron Configurations Are a way of writing out where all the electrons are in an atom. It specifies the orbital, sublevel, and how many electrons are in the sublevel.

Order of filling

Rules for writing electron configurations Pauli exclusion principle  Each “room” can hold a maximum of 2 electrons, but they must be spinning in opposite directions. Aufbau Principle  Electrons enter orbital in order of increasing energy. Hund’s Rule  One electron must fill each “room” in a sublevel before there can be 2.

Examples Nitrogen  1s 2 2s 2 2p 3 Iron  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6

Exceptions to the rules. Chromium  1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 5 Molybdenum  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 4d 5 Tungsten  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 1 5d 5 Copper  1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 10 Silver  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 4d 10 Gold  1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 1 5d 10

The Periodic Table and Noble Gas Configurations Noble gas configurations are a short hand way of writing electron configurations & the Periodic Table can be used to help you write them!

Let’s try some! Nitrogen  Electron configuration - 1s 2 2s 2 2p 3  Noble Gas configuration – [He] 2s 2 2p 3 Iron  Electron configuration - 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6  Noble Gas configuration – [Ar] 4s 2 3d 6