E LECTRONS IN A TOMS Orbital Diagrams and Configurations

R EVIEW What is the “ address” of electrons arrangements starting with the principle energy level? Principle Quantum Number, 1,2,3,4,5,6,7 Sublevels are s, p, d, f There can be at most 2 electrons per orbital. Electron spin + or -

R EVIEW Name the four sublevels of electron configurations, how many orbitals and electrons each has: sublevelorbitalsnumber of e- s12 p36 d510 f714

E LECTRON C ONFIGURATIONS The way in which electrons are arranged around atoms are called electron configurations

E LECTRON C ONFIGURATIONS Since all systems proceed toward the lowest energy state (i.e. water running downhill), electrons fill orbitals to form the most energetically stable arrangement

E LECTRON C ONFIGURATIONS There are three rules that allow us to find these configurations for atoms. 1. Aufbau Principle: Electrons enter orbitals of lowest energy first.

E LECTRON C ONFIGURATIONS There are three rules that allow us to find these configurations for atoms. 1. Aufbau Principle: Electrons enter orbitals of lowest energy first. 2. Pauli Exclusion Principle: An atomic orbital can only hold 2 electrons

E LECTRON C ONFIGURATIONS There are three rules that allow us to find these configurations for atoms. 1. Aufbau Principle: Electrons enter orbitals of lowest energy first. 2. Pauli Exclusion Principle: An atomic orbital can only hold 2 electrons 3. Hund’s Rule: Each orbital of an energy level must have one electron of a particular spin before electrons of opposite spin can be added

O RBITAL D IAGRAMS An orbital diagram can illustrate the arrangement of electrons by showing each atomic orbital occupied by electrons 1.Afbau = lowest energy first 2.Pauli = only 2 e- per orbital 3.Hund = fill one spin before adding the opposite

O RBITAL D IAGRAMS Hydrogen has ____ electrons?

O RBITAL D IAGRAMS Helium has ___ electrons?

O RBITAL D IAGRAMS Carbon has ____ electrons

O RBITAL D IAGRAMS Nitrogen has 7 electrons

O RBITAL D IAGRAMS Oxygen has _____ electrons

O RBITAL D IAGRAMS Fluorine has ____ electrons

O RBITAL D IAGRAMS Neon has ____ electrons

O RBITAL D IAGRAMS Iron has 26 electrons Just remember any d level is one level below the s

O RBITAL D IAGRAMS EXTRA PRACTICE Phosphorus has ____ electrons

O RBITAL D IAGRAMS EXTRA PRACTICE Chromium has 24 electrons 24 Cr Just remember any d level is one level below the s

T HE ORDER THAT THE ELECTRON ORBITALS ARE FILLED CAN BE SUMMARIZED USING A DIAGONAL DIAGRAM. 1s 2s2p 3s3p3d 4s4p4d4f 5s5p5d5f 6s6p6d6f 7s7p

T HE ORDER THAT THE ELECTRON ORBITALS ARE FILLED CAN BE SUMMARIZED USING A DIAGONAL DIAGRAM. 1s 2s2p 3s3p3d 4s4p4d4f 5s5p5d5f 6s6p6d6f 7s7p

E LECTRON C ONFIGURATIONS A SHORTHAND WAY TO SHOW HOW ELECTRONS ARE ARRANGED. 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 1 = principle energy level (period) s, p, d = sublevel superscript = number of electrons

E LECTRON C ONFIGURATIONS E XAMPLES ( ABBREVIATED / UNABBREVIATED ) Oxygen Fluorine Phosphorus Potassium Chromium

T HE P ERIODIC T ABLE FOLLOWS ELECTRON CONFIGURATION The form (shape) of the periodic table is closely related to the electron configuration of the atoms of the elements. The outermost electrons determine most of the chemistry of an element. For example: all the Alkali metals have notable similarities in their chemical properties LithiumLi1s 2 2s 1 SodiumNa[Ne]3s 1 PotassiumK[Ar]4s 1

S UMMARY The way in which electrons are arranged around atoms are called electron configurations 1. Aufbau Principle: lowest energy first. 2. Pauli Exclusion Principle: 2 electrons per orbital 3. Hund’s Rule: Each orbital must have one electron spin before opposite spin can be added orbital diagram shows how each atomic orbital is occupied by electrons The order orbitals are filled is shown by the diagonal diagram Electron configuration shows the electron arrangement.

MISC GRAPHICS