The Electron Configuration

C12-2-06 ELECTRON CONFIGURATION OUTCOME QUESTION(S): C12-2-06 ELECTRON CONFIGURATION Relate the electron configuration of an element to its valence electron(s) and its position on the Periodic Table. Include: quantum energy level, shapes, and orbitals. Write the electron configuration for a variety of atoms and ions using the 3 configuration laws. Include: shorthand notation and valence configuration Vocabulary & Concepts  Pauli Exclusion Principle Hund Rule Aufbau Principle

 Electron Configuration These are the two ways of representing electron location – we will focus on Electron Configuration more often  Orbital Box Diagrams 1s 2s 2p 3s 3p 3d 4s

 Electron Configuration of Zn2+ 1s2 2s2 2p6 3s2 3p6 3d10  Electron Configuration of Zn2+ n = 2 2e- 8e- 18e- n = 1 2e- 8e- 8e- OLD way NEW way

There are 3 main rules for “placing” electrons in configuration NUCLEUS There are 3 main rules for “placing” electrons in configuration 1s Level Shapes orbitals e- capacity 1 s 1 = 1 2 s,p 1+3 = 4 8 3 s,p,d 1+3+5 = 9 18 4 s,p,d,f 1+3+5+7 = 16 32 n n types n2 2n2 2s 2p 3s 3p 3d 4s 4p 4d 4f

Use up (↑) and down arrows (↓) to indicate opposite spin 1. Pauli Exclusion Principle Electrons are constantly spinning which creates a magnetic field Only two electrons can occupy the same orbital and only if they have opposite spins Use up (↑) and down arrows (↓) to indicate opposite spin

2. Aufbau Principle Unexcited electrons fill the lowest, most stable, energy orbital available – ground state. This is no different from the “old” model – fill the lowest shell before moving to outer shells

The “get your own room” principle – no one wants a bunkmate 3. Hund rule Electrons must enter empty orbitals of equal energy first before joining occupied orbitals. The “get your own room” principle – no one wants a bunkmate

Periodic Table actually displays the Aufbau principle for electron configuration of elements. Task: find the element needed, consider the total number of electrons, and use the configuration pattern of the table

Carbon has all the electrons of previous elements plus 1 more Draw orbital box / electron configuration for C: move along the table writing the configuration C 1s 2s 2p C: 1s2 2s2 2p2 Carbon has all the electrons of previous elements plus 1 more

Notice we passed the configuration of Carbon… Draw orbital box / electron configuration for Mg: move along the table writing the configuration Mg Notice we passed the configuration of Carbon… 1s 2s 2p 3s Mg: 1s2 2s2 2p6 3s2

“Germanium has all the electrons of Argon plus these more” Draw electron config for germanium: Ge – atomic number 32 Ge: 4s2 3d10 4p2 1s2 2s2 2p6 3s2 3p6 [Ar] Orbits fill in increasing energy: notice the “d” levels fill out of order… Shorthand notation uses noble gas “kernels.” Ge: [Ar] 4s2 3d10 4p2 “Germanium has all the electrons of Argon plus these more”

Find the last filled Noble Gas to use as the kernel Write the shorthand configurations for Mn and Ag. 1 2 3 4 5 Find the last filled Noble Gas to use as the kernel Mn: [Ar] 4s2 3d5 Ag: [Kr] 5s2 4d9

Valence configuration - 2s2 2p5 Valence configuration includes the electrons in the outer-most or highest quantum level (n). F = 9 electrons 1s2 2s2 2p5 Valence configuration - 2s2 2p5 It’s not just the last ones, but the total electrons in the outer quantum level Ge = 32 electrons 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2 Valence configuration - 4s2 4p2

Valence electrons are removed from the highest quantum level F-1 = 9 electrons + 1 gained 1s2 2s2 2p5 The ION configuration is 1s2 2s2 2p6 Valence electrons are removed from the highest quantum level Fe+2 = 26 electrons – 2 lost 1s2 2s2 2p6 3s2 3p6 4s2 3d6 The ION configuration is 1s2 2s2 2p6 3s2 3p6 3d6

Some exceptions to the rule:

Half-filled and completely filled orbitals have extra stability Electron Promotion Half-filled and completely filled orbitals have extra stability Atoms will “promote” similar electrons to improve overall stability Look for configurations ending in “p2” ,“p5” OR “d4” ,“d9” - one electron away from being half or complete filled…”

*Promotion accounts for multiple ionization states (Fe+2, Fe+3…) Cr: [Ar] 4s2 3d4 Cu: [Ar] 4s2 3d9 4s 3d 4s 3d Actual configurations: Cr: [Ar] 4s1 3d5 Cu: [Ar] 4s1 3d10 *Promotion accounts for multiple ionization states (Fe+2, Fe+3…) Think of this as moving a CFO into a CEO at a company – you don’t move the mailperson…

C12-2-06 ELECTRON CONFIGURATION CAN YOU / HAVE YOU? C12-2-06 ELECTRON CONFIGURATION Relate the electron configuration of an element to its valence electron(s) and its position on the Periodic Table. Include: quantum energy level, shapes, and orbitals. Write the electron configuration for a variety of atoms and ions using the 3 configuration laws. Include: shorthand notation and valence configuration Vocabulary & Concepts  Pauli Exclusion Principle Hund Rule Aufbau Principle