Chapter 6 Part 3; Many-electron atoms Read: BLB 6.7 6.9 HW: BLB 6:59,63,64,67,71b-d,74,75,90,97; Packet 6:10 14 Know: s & atoms with many electrons Spin quantum number m s o Pauli exclusion principle o Hund's Rule Electron Configurations using periodic table Summary s Allowed for electrons in atom. Describes of electrons in these energy states. number shape? name of orbitals? ------------------------------------------------------- s p d f QUANTUM NUMBERS n principal l azimuthal m l magnetic defines? Dr. Lori Stepan Van Der Sluys 1 Chapter 6 Part 3 Dr. Lori Stepan Van Der Sluys 2 Chapter 6 Part 3
Shells, Subshells and s Subshell Ex:3s defined by 2 Quantum Numbers (n, l) n=3, l=0 Subshell Ex: 3p defined by 2 Quantum Numbers (n, l) n=3, l=1 Shell Ex: 3rd shell defined by one Quantum Number (n) n=1 Subshell Ex: 3d defined by 2 Quantum Numbers (n, l) n=3, l=2 Ex:3s defined by 3 Quantum Numbers (n, l, ml) n=3, l=0, ml=0 Ex:3px defined by 3 Quantum # (n, m, ml) n=3, l=1, ml=? Ex:3pz n=3, l=1, ml=? Ex:3py defined by 3 Quantum # (n, m, ml) n=3, l=1, ml=? LRSVDS Chem 110 Chapter 6 Part 3 3 Ex:3dxy n=3, l=2, ml=? Ex:3dxz n=3, l=2, ml=? Ex:3dx2-y2 n=3, l=2, ml=? Ex:3dz2 n=3, l=2, ml=? Ex:3dyz n=3, l=2, ml=? Which quantum numbers are needed to define the subshell? 1 n only 2 n and l 3 l only 4 m l only 5 l and m l 6 n, l, and m l LRSVDS Chem 110 Chapter 6 Part 3 4
How are shells, subshells and orbitals related to energy? Energy Levels in the Hydrogen Atom Energy Levels in Many Electron Atoms Why? LRSVDS Chem 110 Chapter 6 Part 3 5 LRSVDS Chem 110 Chapter 6 Part 3 6
ORBITAL ENERGIES energy is: the energy needed to remove an electron from the orbital (positive) or the energy released when an electron goes into the empty orbital (negative). H atom: Energy does not depend on l or m l 2 1 E( n) = RH n 1 e atom with nuclear charge Z (He +, Li +2 ) Z E( n) = RH n Multi-electron atom: where : Z eff = effective nuclear charge Z eff = Z S S(n, l) S(n, l) = screening 2 Zeff ( n, l) = RH E n 2 Screening and Effective Charge See section 7.2 Electrons in inner orbitals act as screens for outer electrons. This is also called shielding. Outer electrons experience a lesser nuclear charge (less attraction), called effective charge (Z eff ) Approximate: Z eff Z m where m = (often use # of core electrons) General Trends in Screening For a given shell (fixed n) s orbital has electron density at nucleus (sees larger Z eff ) and has lower energy p orbital has no electron density at the nucleus and has higher energy screening increases: s < p < d E increases: E s < E p < E d LRSVDS Chem 110 Chapter 6 Part 3 7 LRSVDS Chem 110 Chapter 6 Part 3 8
Shielding Affects the Ordering of Energy Levels Electron spin Stern-Gerlach experiment neutral atoms (electrons) seem to possess magnetic moment that is quantized enter another quantum number spin magnetic quantum number: (m s ) How do the electrons fill the orbitals? In which order? How many electrons can go into an orbital? m s = + up m s = down LRSVDS Chem 110 Chapter 6 Part 3 9 LRSVDS Chem 110 Chapter 6 Part 3 10
More Complete Description of An Electron an electron in an atom is described by quantum numbers: Pauli exclusion principle: no two e in an atom can have the same four quantum numbers Consequences of the Pauli exclusion principle: each orbital can have a maximum of two e, each with opposite spin # of maximum # subshell orbitals of electrons s (l = ) p (l = ) d (l = ) f (l = ) Look at the periodic table! ELECTRON CONFIGURATIONS s are filled sequentially, lowest energy orbitals fill first: Aufbau principle (or building up principle) H Li Na He Be B C N O F Ne Now we have a problem: What is the electron configuration of carbon? Carbon 1s 2 2s 2 2p 2 1s 2 2s 2 2p x 2p y 2p z or 1s 2 2s 2 2p x 2p y 2p z LRSVDS Chem 110 Chapter 6 Part 3 11 LRSVDS Chem 110 Chapter 6 Part 3 12
Hund s rule fill set of degenerate orbitals (subshells) to keep maximum number of spins (parallel) minimizes electron-electron repulsions, thereby energy LRSVDS Chem 110 Chapter 6 Part 3 14 LRSVDS Chem 110 Chapter 6 Part 3 13
Electron Configurations past First Row Ne 1s 2 2s 2 2p 6 [Ne] Na 1s 2 2s 2 2p 6 3s [Ne]3s Mg [Ne] 3s 2 Al [Ne] 3s 2 3p Si [Ne] 3s 2 3p 2 P [Ne] 3s 2 3p 3 S [Ne] 3s 2 3p 4 Cl [Ne] 3s 2 3p 5 Ar [Ne] 3s 2 3p 6 filled subshell K [Ne] 3s 2 3p 6 4s new shell (row) Ca [Ne] 3s 2 3p 6 4s 2 Ca 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 Transition Metal Electron Configurations 4s fills 3d Exception: Cr and Cu (know these 2 exceptions!); Sc [Ar] 4s 2 3d 1 Ti [Ar] 4s 2 3d 2 V [Ar] 4s 2 3d 3 Cr [Ar] 4s 1 3d 5 half filled subshells Mn [Ar] 4s 2 3d 5 Fe [Ar] 4s 2 3d 6 Co [Ar] 4s 2 3d 7 Ni [Ar] 4s 2 3d 8 Cu [Ar] 4s 1 3d 10 filled d-subshell Zn [Ar] 4s 2 3d 10 [Ar] 4s 2 Core valence or or inner-shell outer-shell electrons electrons know the first row of transition metals as well as main group LRSVDS Chem 110 Chapter 6 Part 3 15 LRSVDS Chem 110 Chapter 6 Part 3 16
Order of filling 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d LRSVDS Chem 110 Chapter 6 Part 3 18 LRSVDS Chem 110 Chapter 6 Part 3 17
Electron Configuration and the Periodic Table Location on Periodic Table is related to electron configuration Elements in the same row (family) have the same valence shell configuration. Example: alkali metals (row 1) have what valence electron configuration? (H) 1s 1 Li [He] 2s 1 Na [Ne] 3s 1 K [Ar] 4s 1 Rb [Kr] 5s 1 Cs [Xe] 6s 1 halogens (F, Cl, Br, I) have outer shell noble gases (inert) have filled outer shell of Valence electrons determine the chemistry! Electron Configurations of the Elements LRSVDS Chem 110 Chapter 6 Part 3 20 LRSVDS Chem 110 Chapter 6 Part 3 19
Before next class: Read: BLB 2.5; 7.1 7.6 HW: BLB 2:35; 7:9,21,25,30,31,41a c,43a,e,f; 46, 49, 57, 91 Sup 7:1 12 Know: screening effects periodic properties atomic and ion sizes isoelectronic series electron configurations of ions ionization energies electron affinities LRSVDS Chem 110 Chapter 6 Part 3 21