Quantum Mechanics quantum mechanics orbitals In quantum mechanics, the electrons occupy specific energy levels (as in Bohr's model) but they also exist within specific probability volumes called orbitals with specific orientations in space. The electrons within each orbital has a distinct spin. n n = The principle quantum number Describes the possible energy levels and pictorially it describes the orbital size. n = 1, 2, 3…. where an orbital with the value of 2 is larger than an orbital with the value of 1. 1s 2s

Quantum Mechanics l l = angular momentum quantum number Describes the "shape" of the orbital and can have values from 0 to n - 1 for each n. orbital designation :s p d f shape : m l = magnetic quantum number l ll Related to the orientation of an orbital in space relative to the other orbitals with the same l quantum numbers. It can have values between l and - l. m s = spin quantum number An electron has either + 1 / 2 or - 1 / 2 spin values; sometimes referred to as spin up and spin down. Too hard to draw see text

ATOMICORBITALS

Electron Configuration Electron configuration is a shorthand notation for describing the arrangement of the electrons about the nucleus. General Format using the quantum numbers: n l e- n l e- RULES: 1. Fill the lowest energy levels first. 1s 2s 2p 3s 3p 4s 3d 4p 2. No more than two electrons per orbital. n = principle quantum number l = angular momentum quantum number e- = number of electrons Lowest

Electron ConfigurationExamples: H:He:Li : H:1s 1 He:1s 2 Li : 1s 2 2s 1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 7 Co: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 7 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5 Br: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5 CORE VALENCE The condensed electron configuration distinguishes the core electrons from the valence electrons. CORE electrons are tightly held to the nucleus and resemble a noble gas configuration. VALENCE electrons are the outer most electrons and are involved in chemical reactions. Examples of the condensed configuration: 3d 7 Li:[He] 2s 1 Co:[Ar] 4s 2 3d 7 3d 10 4p 5 Br:[Ar] 4s 2 3d 10 4p 5

Orbital Shapes

Electron Configuration Practice Problems 1. Give the full electron configuration: C ONe Na Si Cl Ar K 2. Give the condensed electron configuration: C ONe Na Si Cl Ar K Answers on next slide

Electron Configuration Answers 1 & 2. Give the full & condensed electron configuration: C 1s 2 2s 2 2p 2 or [He] 2s 2 2p 2 O 1s 2 2s 2 2p 4 or [He] 2s 2 2p 2 Ne 1s 2 2s 2 2p 6 or [Ne] Na 1s 2 2s 2 2p 6 3s 1 or [Ne] 3s 1 Si 1s 2 2s 2 2p 6 3s 2 3p 2 or [Ne] 3s 2 3p 2 Cl 1s 2 2s 2 2p 6 3s 2 3p 5 or [Ne] 3s 2 3p 5 Ar 1s 2 2s 2 2p 6 3s 2 3p 6 or [Ar] K 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 or [Ar]4s 1

Orbital Diagrams Orbital diagrams are written in order of increasing energy levels starting with the lowest energy level the 1s orbital. ___ ___ ___ 4p ___ ___ ___ ___ ___ 3d ___ 4s ___ ___ ___ 3p ___ 3s ___ ___ ___ 2p ___ 2s ___ 1s RULES: (1) fill the lowest energy level first (2) fill each orbital in a subshell with one electron first before you double up. (3) Completely fill each subshell before proceeding to the next energy level. Remember the order!!

Orbital Diagrams Practice Problems 1. Fill in the orbital diagrams for: C ONe Na Si Cl Ar K ___ ___ ___ 4p __ __ __ __ __ 3d ___ 4s ___ ___ ___ 3p ___ 3s ___ ___ ___ 2p___ 2s___ 1s

Orbital Diagrams Practice Problem Answers Fill in the orbital diagrams for: C O ___ ___ ___ 4p __ __ __ __ __ 3d ___ 4s ___ ___ ___ 3p ___ 3s ___ ___ ___ 2p___ 2s___ 1s

Orbital Diagrams Practice Problem Answers Fill in the orbital diagrams for: Ne Na ___ ___ ___ 4p __ __ __ __ __ 3d ___ 4s ___ ___ ___ 3p ___ 3s ___ ___ ___ 2p___ 2s___ 1s

Orbital Diagrams Practice Problem Answers Fill in the orbital diagrams for: Si Cl Si Cl___ ___ ___ 4p __ __ __ __ __ 3d ___ 4s ___ ___ ___ 3p ___ 3s ___ ___ ___ 2p___ 2s___ 1s

Orbital Diagrams G roup Study Problems Fill in the orbital diagrams and then write the electron configuration (both full and condensed) for: BFCaPSAsZnPb ___ ___ ___ 4p __ __ __ __ __ 3d ___ 4s ___ ___ ___ 3p ___ 3s ___ ___ ___ 2p ___ 2s ___ 1s