Electron Configuration Where are the electrons?

Energy Level Diagram Shell 4 3 orbitals 2 subshells 1

Rules to follow when filling orbitals: Fill orbitals from lowest to highest energy (Aufbau Principle) Place one electron in each orbital of a sub-shell When each orbital of a sub-shell has one electron, go back and pair the electrons (Hund’s Rule) If two electrons are in a orbital, they must have opposite spin (Pauli Exclusion Principle)

electron-electron repulsion These rules ensure that the electron configuration gives the ___________ energy, most __________ atom by reducing ________________________________. lowest stable electron-electron repulsion

More About Shells Shell 4 3 2 1 1s22s22p63s23p64s23d104p6 2 8 8 18

How can you write the electron configuration without the energy level diagram???

1s 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 5d 6p 6d 7s 4f 5f

Ar: 1s2 2s2 2p6 3s2 3p6 3p5 3p3 3p1 3p2 3p4

Ga: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p1

Ag: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d9

Rn: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6

K [Ar] 1s2 2s2 2p6 3s2 3p6 4s1 1s2 2s2 2p6 3s2 3p6 Ti [Ar] 4s2 3d2 1s2 2s2 2p6 3s2 3p6 Ni [Ar] 4s2 3d8 1s2 2s2 2p6 3s2 3p6 Ga [Ar] 4s2 3d10 4p1 1s2 2s2 2p6 3s2 3p6 Kr [Ar] 4s2 3d10 4p6 Ar

[Ar] 4s2 3d 5

Example: Write the electron configuration for Ga using core notation. Closest previous noble gas element: ______ Core notation:___________________ Ar [Ar] 4s23d104p1

Practice: Write the electron configuration for the following elements. Zn _______________________________ K ________________________________ Kr _______________________________

There are 2 exceptions to the electron configuration of elements up to Kr:

What you would expect for Cr

In Reality

What you would expect for Cu

In Reality

Reason: ½ filled and completely filled subshells are more stable than partially filled subshells, and in Cr and Cu, it only takes one electron to achieve this stability in the 3d subshell Expected Reality Cr [Ar] 4s23d4 [Ar] 4s13d5 Cu [Ar] 4s23d9 [Ar] 4s13d10