Kull Spring07 Lesson 22 Ch 7/8 1 CHAPTER 8 Atomic Electron Configurations and Chemical Periodicity Road Map - Lesson 22 Recap of Ch 7 problems Area of Focus : Chapter 8 The Exclusion Principle – introduction of the 4 th q.n. Electron Spin Subshell filling order Atomic electron configuration

Kull Spring07 Lesson 22 Ch 7/8 2Equations  wavelength x frequency  speed of light = wavelength x frequency c = λ X = 3.00 x 10 8 m/s  = nh(c/ )  E = nh = nh(c/ ) n= positive integer Planck’s constant(h) = x 10 –34 J s    E atom = E emitted (or absorbed) radiation =  nh  Rydberg equation = R  n 2 > n 1  R = x 10 7 m -1  ΔE = E final – E initial = –2.18 x 10–18 J   E photon = E state A – E state B = hν

Kull Spring07 Lesson 22 Ch 7/8 3 Quantum mechanics Quantum number Values Total number n – shell/level 1,2,3, … ∞ n = # subshells n 2 = # orbitals in a shell - subshell/ sublevel ℓ - subshell/ sublevel 0, 1,… n-1 n-1 m ℓ - orbital - - ℓ, 0, + ℓ 2 2 ℓ +1 (orbitals in a subshell) m s - spin + ½, -½ 2 possible

Kull Spring07 Lesson 22 Ch 7/8 4   According to the quantum mechanical treatment of the hydrogen atom, which set of quantum numbers is not allowed? A) n = 3, ℓ = 2, m ℓ = 0 B) n = 3, ℓ = 0, m ℓ = 0 C) n = 3, ℓ = 1, m ℓ = 1 D) n = 3, ℓ = 1, m ℓ = -1 E) n = 3, ℓ = 1, m ℓ = 2 Practice Problem 22-1

Kull Spring07 Lesson 22 Ch 7/8 5   According to the quantum mechanical treatment of the hydrogen atom, which set of quantum numbers is not allowed? A) n = 3, ℓ = 2, m ℓ = 0 B) n = 3, ℓ = 0, m ℓ = 0 C) n = 3, ℓ = 1, m ℓ = 1 D) n = 3, ℓ = 1, m ℓ = -1 E) n = 3, ℓ = 1, m ℓ = 2 Practice Problem 22-1 Answer

Kull Spring07 Lesson 22 Ch 7/8 6   For an excited hydrogen atom with the quantum number n equal to 9, which of the following statements is true? A) The energy of the atom is less than the energy for the state in which n is equal to 8. B) If ℓ = 0, there are nine possible values for the magnetic quantum number m ℓ. C) The smallest value of the magnetic quantum number m ℓ is -9. D) The electron must be in one of the p orbitals. E) The angular momentum quantum number ℓ can have any of the values 0, 1, 2, 3, 4, 5, 6, 7, 8. Practice Problem 22-2

Kull Spring07 Lesson 22 Ch 7/8 7   For an excited hydrogen atom with the quantum number n equal to 9, which of the following statements is true? A) The energy of the atom is less than the energy for the state in which n is equal to 8. B) If ℓ = 0, there are nine possible values for the magnetic quantum number m ℓ. C) The smallest value of the magnetic quantum number m ℓ is -9. D) The electron must be in one of the p orbitals. E) The angular momentum quantum number ℓ can have any of the values 0, 1, 2, 3, 4, 5, 6, 7, 8. Practice Problem 22-2 Answer

Kull Spring07 Lesson 22 Ch 7/8 8   According to the quantum-mechanical model, how many orbitals in a given atom have n = 3? A) 4 B) 7 C) 9 D) 10 E) 18 Practice Problem 22-3

Kull Spring07 Lesson 22 Ch 7/8 9   According to the quantum-mechanical model, how many orbitals in a given atom have n = 3? A) 4 B) 7 C) 9 D) 10 E) 18 Practice Problem 22-3 Answer

Kull Spring07 Lesson 22 Ch 7/8 10 Chapter 8  The Exclusion Principle – introduction of the 4 th q.n.  Hund’s rule  Electron Spin  Subshell filling order  Atomic electron configuration

Kull Spring07 Lesson 22 Ch 7/8 11 Chapter 8  Pauli Exclusion Principle - No two electrons in the same atom can have the same set of 4 quantum numbers.  each electron has a unique address.  HUND’S RULE - When placing electrons in a set of orbitals having the same energy, we place them singly as long as possible.   aufbau principle is the building up process that results in ground-state electron configurations

Kull Spring07 Lesson 22 Ch 7/8 12 Electron Configurations and the Periodic Table Active Figure 8.7

Kull Spring07 Lesson 22 Ch 7/8 13 Electron Filling Order Figure 8.5

Kull Spring07 Lesson 22 Ch 7/8 14 Quantum mechanics Quantum number Values Total number n – shell/level 1,2,3, … ∞ n = # subshells n 2 = # orbitals in a shell - subshell/ sublevel ℓ - subshell/ sublevel 0, 1,… n-1 n-1 m ℓ - orbital - - ℓ, 0, + ℓ 2 2 ℓ +1 (orbitals in a subshell) m s - spin + ½, -½ 2 possible

Kull Spring07 Lesson 22 Ch 7/8 15 Writing Atomic Electron Configurations Two ways of writing configs.  the spdf notation. 2) the orbital box notation. Two ways of writing configs.  the spdf notation. 2) the orbital box notation. 1 1 s value of n value of l no. of electrons spdf notation for H, atomic number = 1 One electron has n = 1, l = 0, m l = 0, m s = + 1/2 Other electron has n = 1, l = 0, m l = 0, m s = - 1/2

Kull Spring07 Lesson 22 Ch 7/8 16 PhosphorusPhosphorus All Group 5A elements have [core ] ns 2 np 3 configurations where n is the period number. Group 5A Atomic number = 15 1s 2 2s 2 2p 6 3s 2 3p 3 [Ne] 3s 2 3p 3 Yellow P Red P

Kull Spring07 Lesson 22 Ch 7/8 17

Kull Spring07 Lesson 22 Ch 7/8 18 PERIODIC TRENDS

Kull Spring07 Lesson 22 Ch 7/8 19 General Periodic Trends  Atomic and ionic size  # electrons  # shells – Larger orbitals, -electrons held less tightly  Ionization energy  Electron affinity  energy involved when an atom gains an electron to form an anion.  Effective nuclear charge  When higher: Electrons held more tightly

Kull Spring07 Lesson 22 Ch 7/8 20 Trends in Atomic Size

Kull Spring07 Lesson 22 Ch 7/8 21 Effective Nuclear Charge, Z*  Z* is the nuclear charge experienced by the outermost electrons.  Z* increases across a period owing to incomplete shielding by inner electrons.  The 2s electron PENETRATES the region occupied by the 1s electron.  2s electron experiences a higher positive charge than expected.  Estimate Z* by --> [ Z - (# inner electrons) ]  Charge felt by 2s e- in Li Z* = = 1  Be Z* = = 2  B Z* = = 3and so on!

Kull Spring07 Lesson 22 Ch 7/8 22 Ion Configurations To form cations, always remove electrons of highest n value first! P [Ne] 3s 2 3p 3 - 3e- ---> P 3+ [Ne] 3s 2 3p 0

Kull Spring07 Lesson 22 Ch 7/8 23 Ion Sizes  CATIONS are SMALLER than the atoms from which they come.  The electron/proton attraction has gone UP and so size DECREASES. Li,152 pm 3e and 3p Li +, 78 pm 2e and 3 p + Forming a cation.

Kull Spring07 Lesson 22 Ch 7/8 24 Ion Sizes  ANIONS are LARGER than the atoms from which they come.  The electron/proton attraction has gone DOWN and so size INCREASES.  Trends in ion sizes are the same as atom sizes. Forming an anion. F, 71 pm 9e and 9p F -, 133 pm 10 e and 9 p -

Kull Spring07 Lesson 22 Ch 7/8 25 Trends in Ion Sizes Active Figure 8.15

Kull Spring07 Lesson 22 Ch 7/8 26 Ionization Energy IE = energy required to remove an electron from an atom in the gas phase. Mg (g) kJ ---> Mg + (g) + e- Mg+ (g) kJ ---> Mg2+ (g) + e- Mg+ has 12 protons and only 11 electrons. Therefore, IE for Mg+ > Mg