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Transcript
Chapter 7 Periodic Properties of the Elements Periodic Table Modern Periodic Table – Dmitri Mendeleev – Elements are arranged in order of atomic number – Organize the table by chemical properties 2 © 2015 Pearson Education, Inc. Periodic Table • Periodicity – Recurring trends in the element properties • Effective nuclear charge – A fundamental property that leads to many of the trends 3 Effective Nuclear Charge • Properties depend on attractions between valence electrons and the nucleus • Electrons are both attracted to the nucleus and repelled by other electrons 4 © 2015 Pearson Education, Inc. Effective Nuclear Charge • Let’s look at an electron’s attraction to the nucleus • Effective nuclear charge, Zeff, – Nuclear charge experienced by the outermost electrons of an atom 5 © 2015 Pearson Education, Inc. Effective Nuclear Charge • Effective nuclear charge, Zeff, – Nuclear charge experienced by the outermost electrons of an atom – Zeff = Z − S •Z is the atomic number •S is a screening constant –usually close to the number of inner electrons • Effective nuclear charge is a periodic property: – – Increases across a period Decreases down a group 6 http://nptel.ac.in/courses/104103069/7 Effective Nuclear Charge • Effective nuclear charge, Zeff, – Nuclear charge experienced by the outermost electrons of an atom – Zeff = Z − S •Z is the atomic number •S is a screening constant –usually close to the number of inner electrons • Effective nuclear charge is a periodic property: – – Increases across a period Decreases down a group 7 http://chem.libretexts.org/@api/deki/files/8872/=Untitled9.jpg?revision=1 Effective Nuclear Charge • Effective nuclear charge, Zeff, – Nuclear charge experienced by the outermost electrons of an atom – Zeff = Z − S •Z is the atomic number •S is a screening constant –usually close to the number of inner electrons • Effective nuclear charge is a periodic property: – – Increases across a period Decreases down a group 8 http://nptel.ac.in/courses/104103069/7 Effective Nuclear Charge • Effective nuclear charge, Zeff, – Nuclear charge experienced by the outermost electrons of an atom – Zeff = Z − S •Z is the atomic number •S is a screening constant –usually close to the number of inner electrons • Effective nuclear charge is a periodic property: – – Increases across a period Decreases down a group 9 https://classconnection.s3.amazonaws.com/933/flashcards/651080/png/z-eff.png SIZES OF ATOMS AND IONS 10 Sizes of Atoms • Atomic radii – Half of two atoms bond length — Decrease from left to right across a period (Zeff ↑) — Increase from top to bottom of a group (n ↑) 11 © 2015 Pearson Education, Inc. EXAMPLE ATOMIC SIZE SKILLBUILDER | Atomic Size Choose the larger atom in each pair. (a) Pb or Po (b) Rb or Na (c) Sn or Bi (d) F or Se Answers: (a) Pb (b) Rb (c) (d) 12 Ion Size • Determined by interatomic distances in ionic compounds 13 Ion Size • Determined by interatomic distances in ionic compounds • Ionic size depends on – the nuclear charge – the number of electrons – the orbitals in which electrons reside 14 http://nptel.ac.in/courses/104103069/7 Ionic Bond: Ion Size • Cations are smaller than their parent atoms: – Repulsions between electrons are reduced • Anions are larger than their parent atoms: – Repulsions between electrons are increased 15 © 2015 Pearson Education, Inc. Ion Size • Isoelectronic series – ions have the same number and configuration of electrons – Ionic size decreases with an increasing nuclear charge Na+: 1s22s22p6 Ne: 1s22s22p6 Cl-: 1s22s22p63s23p6 Ar: 1s22s22p63s23p6 16 Ion Size • Isoelectronic series – ions have the same number and configuration of electrons – Ionic size decreases with an increasing nuclear charge An Isoelectronic Series (10 electrons) O2– 1.26 Å F– 1.19 Å Na+ 1.16 Å Mg2+ 0.86 Å Al3+ 0.68 Å • Note increasing nuclear charge with decreasing ionic radius as atomic number increases 17 EXAMPLE ATOMIC SIZE Choose the larger atom in each pair. (a) C or O (b) Li or K (c) C or Al (d) Se or I SOLUTION (a) C or O Carbon atoms are larger than O atoms because, as you trace the path between C and O on the periodic table, you move to the right within the same period. Atomic size decreases as you go to the right. 18 EXAMPLE ATOMIC SIZE Choose the larger atom in each pair. (a) C or O (b) Li or K (c) C or Al (d) Se or I SOLUTION (b) Li or K Potassium atoms are larger than Li atoms because, as you trace the path between Li and K on the periodic table, you move down a column. Atomic size increases as you go down a column. 19 EXAMPLE ATOMIC SIZE Choose the larger atom in each pair. (a) C or O (b) Li or K (c) C or Al (d) Se or I 20 EXAMPLE ATOMIC SIZE Choose the larger atom in each pair. (a) C or O (b) Li or K (c) C or Al (d) Se or I 21 IONIZATION ENERGY 22 Ionization Energy (I) • Ionization energy – Minimum energy required to remove an electron from the ground state of a gaseous atom or ion – First ionization energy is that energy required to remove the first electron – Second ionization energy is that energy required to remove the second electron, etc 23 https://www.thunderbolts.info/wp/wp-content/uploads/2011/08/ionization-image.jpg Ionization Energy • Requires more energy to remove each successive electron • Higher the ionization energy, the more difficult it is to remove an electron • When all valence electrons have been removed, it takes a great deal more energy to remove the next electron 24 © 2015 Pearson Education, Inc. Periodic Trends in First Ionization Energy (I1) • • • • I1 generally increases across a period I1 generally increases up a group The s- and p-block elements show a larger elements show aof values for I range 1 The d-block generally increases slowly across the period 25 © 2015 Pearson Education, Inc. Factors that Influence Ionization Energy • • Smaller atoms have higher I values I values depend on effective nuclear charge and average distance of the electron from the nucleus 26 https://s-media-cache-ak0.pinimg.com/564x/38/1b/8c/381b8cbc58ea1fa59e68a7305a884eb9.jpg First Ionization Energy: Irregularities • Trend is not followed when the added valence electron – enters a new sublevel (higher energy subshell) – is the first electron to pair in one orbital of the sublevel (electron repulsions lower energy) 27 © 2015 Pearson Education, Inc. http://wps.prenhall.com/wps/media/objects/3081/3155273/blb0703/bl07fg06.jpg Example First Ionization Energy On the basis of periodic trends, determine the element with the higher first ionization energy in each pair (if possible). (a) Al or S (b) As or Sb (c) N or Si (d) O or Cl Solution (a) Al or S S has a higher first ionization energy than Al because, as you trace the path between Al and S on the periodic table, you move to the right within the same row. Ionization energy increases as you go to the right because of increasing effective nuclear charge. Example First Ionization Energy On the basis of periodic trends, determine the element with the higher first ionization energy in each pair (if possible). (a) Al or S (b) As or Sb (c) N or Si (d) O or Cl Solution (b) As or Sb As has a higher first ionization energy than Sb because, as you trace the path between As and Sb on the periodic table, you move down a column. Ionization energy decreases as you go down a column because of the increasing size of orbitals with increasing n. Example First Ionization Energy On the basis of periodic trends, determine the element with the higher first ionization energy in each pair (if possible). (a) Al or S (b) As or Sb (c) N or Si (d) O or Cl Example First Ionization Energy On the basis of periodic trends, determine the element with the higher first ionization energy in each pair (if possible). (a) Al or S (b) As or Sb (c) N or Si (d) O or Cl ELECTRON AFFINITY 32 Electron Affinity • Electron affinity – Energy change accompanying the addition of an electron to a gaseous atom Cl + e− Cl− – Typically exothermic, so negative value 33 General Trend in Electron Affinity • Trends – Not much change in a group – Increases across a period – Three notable exceptions include: 1) 2) 3) Group 2A: s sublevel is full! Group 5A: p sublevel is half-full! Group 8A: p sublevel is full! 34 © 2015 Pearson Education, Inc. The correct order of increasing electron affinity (most negative least negative) is a. b. c. d. O < Cl < B < C. O < Cl < C < B. Cl < O < C < B. Cl < O < B < C. The correct order of increasing electron affinity (most negative least negative) is a. b. c. d. O < Cl < B < C. O < Cl < C < B. Cl < O < C < B. Cl < O < B < C. METALS, NONMETALS, AND METALLOIDS 37 Metal, Nonmetals, and Metalloids 38 © 2015 Pearson Education, Inc. Metal, Nonmetals, and Metalloids Properties of metals: Shiny luster Conduct heat and electricity Malleable and ductile Solids at room temperature (except mercury) Low ionization energies/form cations easily 39 © 2015 Pearson Education, Inc. Metal, Nonmetals, and Metalloids Properties of nonmetals: Solid, liquid, or gas (depends on element) Solids are dull, brittle, poor conductors Large negative electronegativity 40 © 2015 Pearson Education, Inc. Metal, Nonmetals, and Metalloids Properties of metalloids: Characteristics of metals and nonmetals Several metalloids are electrical semiconductors (computer chips) 41 © 2015 Pearson Education, Inc. Metalloids • Metalloids have some characteristics of metals and some of nonmetals. • Several metalloids are electrical semiconductors (computer chips). 42 Metals vs Nonmetals • Metals tend to form cations • Nonmetals tend to form anions 43 © 2015 Pearson Education, Inc. Metal Chemistry • Compounds the contain metals and nonmetals tend to be ionic • Metal oxides tend to be basic 44 © 2015 Pearson Education, Inc. Nonmetal Chemistry • Substances containing only nonmetals are molecular compounds • Most nonmetal oxides are acidic 45 © 2015 Pearson Education, Inc. EXAMPLE METALLIC CHARACTER Choose the more metallic element from each pair. (a) Sn or Te (b) Si or Sn (c) Br or Te (d) Se or I SOLUTION (a) Sn or Te Sn is more metallic than Te because, as you trace the path between Sn and Te on the periodic table, you move to the right within the same period. Metallic character decreases as you go to the right. 46 EXAMPLE METALLIC CHARACTER Choose the more metallic element from each pair. (a) Sn or Te (b) Si or Sn (c) Br or Te (d) Se or I SOLUTION (b) Si or Sn Sn is more metallic than Si because, as you trace the path between Si and Sn on the periodic table, you move down a column. Metallic character increases as you go down a column. 47 EXAMPLE METALLIC CHARACTER Choose the more metallic element from each pair. (a) Sn or Te (b) Si or Sn (c) Br or Te (d) Se or I 48 EXAMPLE METALLIC CHARACTER Choose the more metallic element from each pair. (a) Sn or Te (b) Si or Sn (c) Br or Te (d) Se or I 49 Alkali Metals • Alkali metals – Soft – Metallic solids • Typical metallic properties (luster, conductivity) 50 © 2015 Pearson Education, Inc. Alkali Metals • Alkali metals – Soft – Metallic solids • Typical metallic properties (luster, conductivity) – Only found in compounds in nature 51 http://www.carondelet.pvt.k12.ca.us/Family/Science/Alkali%20Metals/cartoon.gif Alkali Metals • Alkali metals – Soft – Metallic solids • Typical metallic properties (luster, conductivity) – Only found in compounds in nature – Low melting points 52 © 2015 Pearson Education, Inc. Alkali Metals • Alkali metals – Soft – Metallic solids • Typical metallic properties (luster, conductivity) – Only found in compounds in nature – Low melting points – Low densities 53 © 2015 Pearson Education, Inc. Alkali Metals • Alkali metals – Soft – Metallic solids • Typical metallic properties (luster, conductivity) – Only found in compounds in nature – Low melting points – Low densities – Low ionization energies 54 © 2015 Pearson Education, Inc. Alkali Metals • Alkali metals – Soft – Metallic solids • Typical metallic properties (luster, conductivity) – Only found in compounds in nature – Low densities – Low melting points – Low ionization energies – Reactions with water are exothermic © 2015 Pearson Education, Inc. 55 Alkali Metals • Alkali metals – Emit characteristic color in a flame • Flame test: Qualitative test © 2015 Pearson Education, Inc. 56 Alkali Metal Chemistry • Lithium reacts with oxygen to make an oxide: 4 Li + O2 2 Li2O • Sodium reacts with oxygen to form a peroxide: 2 Na + O2 Na2O2 • K, Rb, and Cs also form superoxides: M + O2 MO2 57 Alkaline Earth Metals • Alkaline Earth Metals – Reaction with water • Beryllium does not react with water • Magnesium reacts readily with steam • Other alkaline earth metals react readily with water – Reactivity tends to increase down the group 58 © 2015 Pearson Education, Inc. Alkaline Earth Metals • Alkaline Earth Metals – Reaction with water • Beryllium does not react with water • Magnesium reacts readily with steam • Other alkaline earth metals react readily with water – Reactivity tends to increase down the group – Emit characteristic color in a flame https://qph.is.quoracdn.net/main-qimg-3337403d76081268fb74f7351c1c7ec5?convert_to_webp=true 59 Alkaline Earth Metals • Alkaline Earth Metals – Higher densities and melting points than alkali metals – Low ionization energies • not as low as alkali metals 60 © 2015 Pearson Education, Inc. Chalcogens • Oxygen, sulfur, and selenium are nonmetals • Tellurium is a metalloid • The radioactive polonium is a metal 61 Halogens • Halogens are typical nonmetals • Have highly negative electron affinities – Exist as anions in nature • React with metals to form metal halides 62 Noble Gases • Noble gases have – – – – Very large ionization energies Positive electron affinities (can’t form stable anions) Relatively unreactive Found as monatomic gases 63 64 EXAMPLE METALLIC CHARACTER Continued SKILLBUILDER | Metallic Character Choose the more metallic element from each pair. (a) Ge or In (b) Ga or Sn (c) P or Bi (d) Bor N Answers: 65 The first Periodic Table was created by a. b. c. d. Amadeo Avogadro. Dmitri Mendeleev. Henry Moseley. Ernest Rutherford. 66 The effective nuclear charge felt by an atom’s valence electrons (X) going from left to right and (Y) going down a column on the periodic table. a. b. c. d. X = increases X = increases X = decreases X = decreases Y = increases Y = decreases Y = increases Y = decreases 67 True or False: The large number of valence electrons in a chlorine atom greatly reduces the effective nuclear charge of the atom. a.True b.False 68 The atom with the smallest atomic radius is a. b. c. d. Ca. Cr. Co. Br. 69 The correct order of increasing atomic radius (smallest largest) is a. b. c. d. Na < Mg < K < Rb. Mg < Na < K < Rb. Rb < K < Na < Mg. Rb < K < Mg < Na. 70 The shortest distance between the nuclei of two identical atoms when they collide is called the ___ radius. a. b. c. d. anionic cationic effective van der Waals 71 The statements below refer to ionic radii. Which statement is FALSE? a. b. c. d. Br1– is larger than Cl1–. Se2– is larger than Br1–. K1+ is larger than Ca2+. Na1+ is larger than K1+. 72 Two ions are isoelectronic if they have the same a. b. c. d. charge. number of protons. number of electrons. number of neutrons. 73 Which set represents an isoelectronic series? a. b. c. d. Ne, Ar, Kr, Xe Al, Si; Ge, As; Sb, Te Se2−, Br−, Rb+, Sr2+ Cu 2+, Ag+, Au 74 When a main-group metal ion loses an electron to form a cation, the ionic radius is ___ the atomic radius. a. b. c. d. greater than less than the same as impossible to predict in relation to 75 The minimum energy needed to remove an electron from an atom in its ground state is called the atom’s a. b. c. d. potential energy. activation energy. electron affinity. ionization energy. 76 The energy change that occurs when an electron is added to an atom is called the atom’s a. b. c. d. potential energy. activation energy. electron affinity. ionization energy. 77 The correct order of increasing first ionization energy (smallest largest) is a. b. c. d. Na < Ca < Al < Sn. Na < Al < Ca < Sn. Na < Al < Sn < Ca. Ca < Na < Sn < Al. 78 The atom with successive ionization energies of 578, 1817, 2745, and 11,577 kJ/mol is a. b. c. d. Al. Na. Mg. P. 79 The correct order of increasing electron affinity (most negative least negative) is a. b. c. d. O < Cl < B < C. O < Cl < C < B. Cl < O < C < B. Cl < O < B < C. 80 Most metal oxides form _______ solutions when dissolved in water. a. b. c. d. acidic basic neutral amphoteric 81 Most nonmetal oxides form _______ solutions when dissolved in water. a. b. c. d. acidic basic neutral amphoteric 82 The metalloid with the least metallic character is a. b. c. d. e. As. B. Ge. Sb. Si. 83 A soft gray solid reacts with water to form a flammable gas and a basic solution. The solid is most likely to be a a. b. c. d. noble gas. halogen. group IIA metal. transition metal. 84 Ozone is an allotrope of which element? a. b. c. d. hydrogen oxygen sulfur chlorine 85 Unknown solid X turns a Bunsen burner flame green and produces a purple color on reaction with NaOCl. X is a. b. c. d. BaI2. BaBr2. SrI2. SrBr2. 86 The noble gases a. b. c. d. are monatomic. have filled s and p subshells. are generally unreactive. All of the above. 87