2-Day AP/Pre-AP Science Conference Corpus Christi Omni-Marina Hotel January 20 & 21, 2006 Atomic Structure and Periodicity John I. Gelder Former Chief Reader AP Chemistry Department of Chemistry Oklahoma State University

Important Web Site Atomioc structure and Periodicity Materials Go to the link for AP Chemistry teachers.

Atomic Structure Topics Properties of light: wavelength, frequency, speed, relationship to energy The hydrogen atom: energy level diagram, emission and absorption of light,hydrogen atom Shell Model: first ionization energies, photoelectron spectra Electron configurations

Periodicity Ionization energyIonization energy Graph of IEGraph of IE Atomic radii Ionic radii Cations Anions Electron affinity

2002 AP Chemistry Exam Use principles of atomic structure and/or chemical bonding to explain each of the following. In each part, your answer must include references to both substance. a)The atomic radius of Li is larger than that of Be. b)The second ionization energy of K is greater than the second ionization energy of Ca.

2002 AP Chemistry Exam Use principles of atomic structure and/or chemical bonding to explain each of the following. In each part, your answer must include references to both substance. a)The atomic radius of Li is larger than that of Be. The electron configuration for Li is 1s 2 2s 1 The electron configuration for Be is 1s 2 2s 2 Both element have their valence electrons in the same shell and are shielded by the same number of electrons. Since Be has a greater nuclear charge it has a smaller atomic radius compared to Li because the valence electrons in Be experience a greater attraction to the nucleus.

2002 AP Chemistry Exam Use principles of atomic structure and/or chemical bonding to explain each of the following. In each part, your answer must include references to both substance. a)The atomic radius of Li is larger than that of Be. The electron configuration for Li is 1s 2 2s 1 The electron configuration for Be is 1s 2 2s 2 The effective nuclear charge experienced by the valence electrons in Li is +1, while the effective nuclear charge experienced by the valence electrons in Be is +2. Since the valence electrons in Be experience a higher ENC, they experience a greater attraction to the nucleus and the atomic radius is smaller for Be compared to Li.

2002 AP Chemistry Exam Use principles of atomic structure and/or chemical bonding to explain each of the following. In each part, your answer must include references to both substance. b)The second ionization energy of K is greater than the second ionization energy of Ca. The electron configuration for K is 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 The electron configuration for Ca is 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 In potassium the second electron is removed from the n = 3 shell. The ENC experienced on the electrons in n = 3 shell is a +9. Such a high ENC means the energy required to remove the second electron is very large. In calcium the second electron is removed from the n = 4 shell. The ENC experienced on the electrons in n = 4 shell is a +2. The much smaller ENC on the second electron removed from Ca means the ionization energy is much lower.

2005 AP Chemistry Exam Use principles of atomic structure, bonding to and/or intermolecular attractive forces to respond to each of the following. Your responses must include specific information about all substances referred to in each question. c)As shown in the table below, the first ionization energies of Si, P and Cl show a trend. (i)For each of the elements, identify the quantum level (n = 1, n = 2, etc.) of the valence electrons in the atom. (ii)Explain the reasons for the trend in first ionization energies. ElementFirst Ionization Energy (kJ mol -1 ) Si786 P1,012 Cl1,252

2005 AP Chemistry Exam Use principles of atomic structure, bonding to and/or intermolecular attractive forces to respond to each of the following. Your responses must include specific information about all substances referred to in each question. c)As shown in the table below, the first ionization energies of Si, P and Cl show a trend. (i)For each of the elements, identify the quantum level (n = 1, n = 2, etc.) of the valence electrons in the atom. n = 3 ElementFirst Ionization Energy (kJ mol -1 ) Si786 P1,012 Cl1,252

2005 AP Chemistry Exam Use principles of atomic structure, bonding to and/or intermolecular attractive forces to respond to each of the following. Your responses must include specific information about all substances referred to in each question. c)As shown in the table below, the first ionization energies of Si, P and Cl show a trend. (ii)Explain the reasons for the trend in first ionization energies. The electron configuration for Si is 1s 2 2s 2 2p 6 3s 2 3p 2 The electron configuration for P is 1s 2 2s 2 2p 6 3s 2 3p 3 The electron configuration for Cl is 1s 2 2s 2 2p 6 3s 2 3p 5 Since the nuclear charge increases from Si to P to Cl, and the valence electrons are shielded by the same number of inner core electrons (10), Cl has the larger IE since the valence electrons in Cl experience the greater attraction to the nucleus. The greater the attraction the greater the energy required to remove an electron. ElementFirst Ionization Energy (kJ mol -1 ) Si786 P1,012 Cl1,252