n = 3 1s 2s 2p 3s 3p 3d n = 2 n = 1

1s 2s 2p 3s 3p 3d Energy Level Sublevels Total Orbitals 1 s 1s 2 s,p NUCLEUS 1s Energy Level Sublevels Total Orbitals 1 s 1s 2 s,p 1s+3p = 4 3 s,p,d 1s+3p+5d = 9 4 s,p,d,f 1s+3p+5d+7f = 16 n n types n2 2s 2p 3s 3p 3d 4s 4p 4d 4f

The Electron Configuration

Explain the pattern of configuration using the Periodic Table. Explain the Aufbau, Pauli and Hund rules. Write the electron configuration or orbital box diagrams for a variety of atoms and ions.

Each orientation for a sublevel contains a maximum of 2 e-. Pauli Exclusion Principle Electrons are constantly spinning which results in a magnetic field. Two electrons can occupy the same orbital only if they have opposite spins. Each orientation for a sublevel contains a maximum of 2 e-.

Energy Level Sublevels Total # e- capacity 1 s 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

n = 3 1s 2s 2p 3s 3p 3d n = 2 n = 1

Aufbau Principle Unexcited electrons fill the lowest, most stable, energy orbital available – ground state. Range of energies contains some overlap between higher principle levels.

Hund rule Electrons must enter empty orbitals of equal energy first before joining occupied orbitals.

Electron Configuration Orbital Box Diagrams 1s 2s 2p 3s 3p 3d 4s

Periodic Table shows orbital filling for the electron configuration of elements. Energy level (n) of valence electrons is the same as the period of the atom. 1 2 3 4 5 6 7

Draw orbital box and electron config for carbon. 1s 2s 2p C: 1s2 2s2 2p2 Draw orbital box and electron config for Mg. 1s 2s 2p 3s Mg: 1s2 2s2 2p6 3s2

Draw electron config for germanium. Ge – atomic number 32 Ge: 4s2 3d10 4p2 1s2 2s2 2p6 3s2 3p6 [Ar] Shorthand notation using noble gas “kernels.” Ge: [Ar] 4s2 3d10 4p2

Use the periodic table to help write the shorthand configurations for Mn and Ag. 1 2 3 4 5 Mn: [Ar] 4s2 3d5 Ag: [Kr] 5s2 4d9

Valence electrons are the electrons found in the outer-most or highest quantum level (n). F = 9 electrons 1s2 2s2 2p5 The valence configuration is 2s2 2p5 Ge = 32 electrons 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2 The valence configuration is 4s2 4p2

F- = 9 electrons + 1 1s2 2s2 2p5 The ION configuration is 1s2 2s2 2p6 Valence electrons also removed from highest quantum level (n) in positive ions. Fe+2 = 26 electrons - 2 1s2 2s2 2p6 3s2 3p6 4s2 3d6 The ION configuration is 1s2 2s2 2p6 3s2 3p6 3d6

Some exceptions to the rule:

Exceptions exist as the energy differences between higher energy sublevels become smaller. Half-filled and completely filled subshells have extra stability – causes electron promotion.

Actual configurations: Cr: [Ar] 4s1 3d5 Cu: [Ar] 4s1 3d10 Electron promotion accounts for multiple ionization states (Fe+2, Fe+3…)

CAN YOU ? / HAVE YOU? Explain the pattern of configuration using the Periodic Table. Explain the Aufbau, Pauli and Hund rules. Write the electron configuration or orbital box diagrams for a variety of atoms and ions.