Electron Configuration Paulis Exclusion Principle Pauli Exclusion Principle

  • Slides: 18
Download presentation
Electron Configuration

Electron Configuration

Pauli’s Exclusion Principle Pauli Exclusion Principle § No two electrons have the same quantum

Pauli’s Exclusion Principle Pauli Exclusion Principle § No two electrons have the same quantum number. (opposite spin) § Maximum electrons in any orbital is two (�� )

 The Pauli exclusion principle summarizes experimental observations that no two electrons in one

The Pauli exclusion principle summarizes experimental observations that no two electrons in one atom can have the same four quantum numbers. That means that within one orbital, electrons must have opposite spin. It also means that one orbital can hold a maximum of two electrons (with opposite spin). 8|3

� An s sublevel, with one orbital, can hold a maximum of 2 electrons.

� An s sublevel, with one orbital, can hold a maximum of 2 electrons. � A p sublevel, with three orbitals, can hold a maximum of 6 electrons. � A d sublevel, with five orbitals, can hold a maximum of 10 electrons. � An f sublevel, with seven orbitals, can hold a maximum of 14 electrons. 8|4

� The building-up principle (or aufbau principle) is a scheme used to reproduce the

� The building-up principle (or aufbau principle) is a scheme used to reproduce the ground-state electron configurations by successively filling sublevels with electrons in a specific order (the building-up order). � This order generally corresponds to filling the orbitals from lowest to highest energy. Note that these energies are the total energy of the atom rather than the energy of the sublevels alone. 8|5

Hund’s Rule RIGHT § When filling degenerate orbital's, electrons will fill an empty orbital

Hund’s Rule RIGHT § When filling degenerate orbital's, electrons will fill an empty orbital before pairing up with another electron. WRONG

Electron Configuration Increasing Energy Electron configuration for Neon ______ ______ 1 s 2 s

Electron Configuration Increasing Energy Electron configuration for Neon ______ ______ 1 s 2 s 2 p Electron Spin Orbital Diagram 1 s 2 2 p 6 Electron Configuration

Electron Configuration �Aufbau diagram shows �O (atomic number 8) ____ each orbital ____ 2

Electron Configuration �Aufbau diagram shows �O (atomic number 8) ____ each orbital ____ 2 s 2 p 1 s electron configuration 1 s 2 2 p 4

Write the electron configuration for Sulfur by using: S (atomic number 16) ____ ____

Write the electron configuration for Sulfur by using: S (atomic number 16) ____ ____ 2 s 2 p ____ 3 s 3 p Orbital Diagram 1 s 1 s 2 2 p 6 3 s 2 3 p 4 Electron configuration How many unpaired electrons does sulfur have? 2 unpaired electrons!

1 s 2 s 3 s 4 s 5 s 6 s 7 s

1 s 2 s 3 s 4 s 5 s 6 s 7 s 2 p 3 p 4 p 5 p 6 p 7 p 3 d 4 d 5 d 6 d 4 f 5 f This results in the following order: 1 s, 2 p , 3 s, 3 p , 4 s, 3 d , 4 p , 5 s, 4 d , 5 p , 6 s, 4 f, 5 d , 6 p , 7 s, 5 f, 6 d , 7 p

Electron Configuration Let’s Practice � P (atomic number 15) 1 s 2 2 p

Electron Configuration Let’s Practice � P (atomic number 15) 1 s 2 2 p 6 3 s 2 3 p 3 � Ca (atomic number 20) 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 � As (atomic number 33) 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 3 � W (atomic number 74) 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 6 5 s 2 4 d 10 5 p 6 6 s 2 4 f 14 5 d 4

Electron Configuration Your Turn N (atomic number 7) 1 s 2 2 p 3

Electron Configuration Your Turn N (atomic number 7) 1 s 2 2 p 3 Na (atomic number 11) 1 s 2 2 p 6 3 s 1 Sb (atomic number 51) 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 6 5 s 2 4 d 10 5 p 3 Cr (atomic number 24) 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 4

� The lowest-energy configuration of an atom is called its ground state. � Any

� The lowest-energy configuration of an atom is called its ground state. � Any other configuration represents an excited state. 8 | 13

� Copper Exceptions Expect: 1 s 2 2 p 6 3 s 2 3

� Copper Exceptions Expect: 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 9 Actual: 1 s 2 2 p 6 3 s 2 3 p 6 4 s 1 3 d 10 � Silver Expect: 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 6 5 s 2 4 d 9 Actual: 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 6 5 s 1 4 d 10 � Chromium Expect: 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 4 Actual: 1 s 2 2 p 6 3 s 2 3 p 6 4 s 1 3 d 5 � Molybdenum Expect: 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 6 5 s 2 4 d 4 Actual: 1 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 6 5 s 1 4 d 5 Exceptions are explained, but not predicted! Atoms are more stable with half full sublevel

� Another way to learn the building-up order is to correlate each sublevel with

� Another way to learn the building-up order is to correlate each sublevel with a position on the periodic table. � The principal quantum number, n, correlates with the period number. � Groups IA and IIA correspond to the s sublevel; Groups IIIA through VIIIA correspond to the p sublevel; the “B” groups correspond to the d sublevel; and the bottom two rows correspond to the f sublevel. This is shown on the next slide. 8 | 15

Energy level equals period number 1 2 3 Energy level equals period number minus

Energy level equals period number 1 2 3 Energy level equals period number minus one 4 5 6 7 Energy level equals period number minus two 8 | 16

Electron Filling in Periodic Table s p 1 2 d 3 4 5 6

Electron Filling in Periodic Table s p 1 2 d 3 4 5 6 * 7 W f * W s

Periodic Table and Electron Configuration Using the periodic table for the filling order of

Periodic Table and Electron Configuration Using the periodic table for the filling order of orbitals, by going in atomic number sequence until you use all the needed electrons in the element