1s2s 2p3s 3p 3d n = 1 n = 2 n = 3

NUCLEUS 1s 2s 2p 3s 3p 3d 4s 4p4d 4f Energy Level SublevelsTotal Orbitals 1s1s1s 2s,p1s+3p = 4 3s,p,d1s+3p+5d = 9 4s,p,d,f1s+3p+5d+7f = 16 nn typesn2n2

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.

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 SublevelsTotal #e - capacity 1s12 2s,p1+3 = 48 3s,p,d1+3+5 = 918 4s,p,d,f = 1632 nn typesn2n2 2n 2

1s2s 2p3s 3p 3d n = 1 n = 2 n = 3

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

Electron Configuration Orbital Box Diagrams 1s2s 2p3s 3p 3d 4s

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

Draw orbital box and electron config for carbon. C: 1s 2 2s 2 2p 2 1s2s 2p3s 3p 3d 4s Draw orbital box and electron config for Mg. Mg: 1s 2 2s 2 2p 6 3s 2 1s2s 2p3s 3p 3d 4s

Draw electron config for germanium. Ge – atomic number 32 Ge: 4s 2 3d 10 4p 2 Shorthand notation using noble gas “kernels.” Ge: [Ar] 4s 2 3d 10 4p 2 1s 2 2s 2 2p 6 3s 2 3p 6 [Ar]

Energy level (n) of valence electrons is the same as the period of the atom. Periodic Table shows orbital filling for the electron configuration of elements.

Use the periodic table to help write the shorthand configurations for Mn and Ag. Mn: [Ar] 4s 2 3d 5 Ag: [Kr] 5s 2 4d 9

Valence electrons are the electrons found in the outer-most or highest quantum level (n). F = 9 electrons 1s 2 2s 2 2p 5 The valence configuration is 2s 2 2p 5 Ge = 32 electrons 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 2 The valence configuration is 4s 2 4p 2

Valence electrons also removed from highest quantum level (n) in positive ions. F - = 9 electrons + 1 1s 2 2s 2 2p 5 The ION configuration is 2s 2 2p 6 Fe +2 = 26 electrons - 2 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 The ION configuration is 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6

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.

Cr: [Ar] 4s 2 3d 4 Cu: [Ar] 4s 2 3d 9 Actual configurations: Cr: [Ar] 4s 1 3d 5 Cu: [Ar] 4s 1 3d 10 4s 3d 4s 3d 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.