ADVANCED CHEMISTRY



CHAPTER 6 SPECIAL TOPIC: PHOTOELECTRON SPECTROSCOPY (PES) - ANSWERSExplain why the peak for Helium is twice as high as the peak for hydrogen.The peak for helium is twice as high as the peak for hydrogen because a helium atom contains two electrons in the 1s orbital, whereas a hydrogen atom contains only 1 electron in the 1s orbital. Explain why helium’s electrons have a higher binding energy (2.37 MJ/mol) than hydrogen’s electrons (1.31 MJ/mol).The helium nucleus contains 2 protons, whereas the hydrogen nucleus only contains 1 proton.The valence electrons of a helium atom experience a greater Coulombic attraction toward the nucleus because of the greater effective nuclear charge. It requires more energy to remove the electrons from a helium atom than it does to remove the electron from a hydrogen atom.Which electrons have higher binding energy…1s electrons or 2s electrons? Explain why.The 1s electrons are closer to the nucleus than the 2s electrons. The 1s electrons experience a stronger attractive force toward the nucleus. The 1s electrons have a higher binding energy than the 2s electrons.Label each peak in the following diagrams as 1s, 2s, or 2p.19771635245181s2s2p1s2s2p17824455794141s2s2p1s2s2p16017142410521s2s2p001s2s2p1432156971421s2s2p001s2s2p12928771068571s2s2p001s2s2pIdentify each of the following elements from the PES diagram.223837581915sodium (Na) 1s22s22p63s10sodium (Na) 1s22s22p63s12190750106680magnesium (Mg) 1s22s22p63s20magnesium (Mg) 1s22s22p63s2202882598425silicon (Si) 1s22s22p63s23p20silicon (Si) 1s22s22p63s23p2208597589535chlorine (Cl) 1s22s22p63s23p50chlorine (Cl) 1s22s22p63s23p52181225104775calcium (Ca) 1s22s22p63s23p64s20calcium (Ca) 1s22s22p63s23p64s2The following questions are taken from AP Chemistry exams.340169517526000The photoelectron spectra at right show theenergy required to remove a 1s electron froma nitrogen atom and from an oxygen atom.Which of the following statements bestaccounts for the peak in the upper spectrumbeing to the right of the peak in the lowerspectrum?(A) Nitrogen atoms have a half-filled p subshell.(B) There are more electron-electron repulsionsin oxygen atoms than in nitrogen atoms.(C)Electrons in the p subshell of oxygen atomsprovide more shielding than electrons in the-8572518288000p subshell of nitrogen atoms.(D)Nitrogen atoms have a smaller nuclear chargethan oxygen atoms.We are comparing two elements that are located in the same period. Oxygen has one more proton than nitrogen. The 1s electrons in oxygen experience a greater attraction toward the nucleus than the 1s electrons in nitrogen.325755018351500A sample containing atoms of C and F wasanalyzed using x-ray photoelectronspectroscopy. The portion of the spectrumshowing the 1s peaks for atoms of the twoelements is shown at right. Which of the following correctly identifies the 1s peak forthe F atoms and provides an appropriateexplanation?(A)Peak X, because F has a smaller first-8572518542000ionization energy than C has.(B)Peak X, because F has a greater nuclearcharge than C has.(C)Peak Y, because F is more electronegativethan C is.(D)Peak Y, because F has a smaller atomic radiusthan C has.We are comparing two elements that are located in the same period. Fluorine has more protons than carbon.. The 1s electrons in fluorine experience a greater attraction toward the nucleus than the 1s electrons in carbon.The photoelectron spectra of the 1s electrons of two isoelectronic species, Ca2+ and Ar, are shown above.Which of the following correctly identifies the species associated with peak X and provides a valid justification?(A)Ar, because it has completely filled energy levels(B)Ar, because its radius is smaller than the radius of Ca2+19050017462500(C)Ca2+, because its nuclear mass is greater than that of Ar(D)Ca2+, because its nucleus has two more protons than the nucleus of Ar hasWe are comparing two isoelectronic species that each have exactly 18 electrons. The Ca2+ ion has more protons than the Ar atom. The 1s electrons in Ca2+ experience a greater attraction toward the nucleus than the 1s electrons in Ar.The complete photoelectron spectra of neutral atoms of two unknown elements, X and Y, are shown above. Which of the following can be inferred from the data?(A)Element X has a greater electronegativity than element Y does.18097519113500(B)Element X has a greater ionization energy than element Y does.(C)Element Y has a greater nuclear charge than element X does.(D)The isotopes of element Y are approximately equal in abundance, but those of element X are not.Element X is lithium (Li) because the electron configuration is 1s22s1.Element Y is beryllium (Be) because the electron configuration is 1s22s2.Beryllium has one more proton than lithium, so it has a greater nuclear charge.20383502095501s2s2p001s2s2pThe complete photoelectron spectrum of an unknown element is shown above. The frequency ranges of different regions of the electromagnetic spectrum are given in the table below.(a)To generate the spectrum above, a source capable of producing electromagnetic radiation with an energy of 7 × 104 kJ per mole of photons was used. Such radiation is from which region of the electromagnetic spectrum? Justify your answer with a calculation.The radiation is in the X-ray region of the spectrum, because the wavelength is 2 × 1017 Hz.2762253937000(b)A student examines the spectrum and proposes that the second ionization energy of the element is3.88 × 103 kJ/mol. To refute the proposed interpretation of the spectrum, identify the following.(i)The subshell from which an electron is removed in the second ionization of an atom of the element2p(ii)The subshell that corresponds to the second peak of the photoelectron spectrum above2s ................
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