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Chapter 3 Atoms and Elements 1 3.1 Elements and Symbols Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Elements 2 Elements are • pure substances that cannot be separated into simpler substances by ordinary laboratory processes • the building blocks of matter • listed on the inside front cover of this text Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Some Elements and Their Names 3 Names come from: • planets • mythological figures • minerals • colors • geographic locations • famous people Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chemical Symbols 4 Chemical Symbols • represent name of element • consist of one to two letters and start with capital 1-Letter Symbols 2-Letter Symbols C carbon Co cobalt N nitrogen Ca calcium F fluorine Al aluminum O oxygen Mg magnesium Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chemical Symbols from Latin Names 5 Ag silver, from argentum Au gold, from aurum Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 6 Write the correct chemical symbols for each of the following elements: A. iodine B. iron C. magnesium D. zinc E. nitrogen Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 7 Write the symbols for each of the following elements: A. iodine = I B. iron = Fe C. magnesium = Mg D. zinc = Zn E. nitrogen =N Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 8 Give the names of the elements with the following symbols: A. P B. Al C. Mn D. H E. K Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 9 Give the names of the elements with the following symbols: A. P = phosphorus B. Al = aluminum C. Mn = manganese D. H = hydrogen E. K = potassium Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 3 Atoms and Elements 10 3.2 The Periodic Table Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Groups and Periods 11 On the periodic table, • elements are arranged according to similar properties • groups contain elements with similar properties in vertical columns • periods are horizontal rows of elements Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Groups and Periods 12 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Periodic Table of Elements 13 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Group Numbers 14 Group numbers • use the letter A for representative elements (Groups 1A–8A) • use the letter B for transition elements (Groups 3B–12B) Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Classification of Groups 15 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Alkali Metals 16 Group 1A, the alkali metals, includes lithium, sodium, potassium, rubidium, and cesium. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Halogens 17 Group 7A, the halogens, includes chlorine, bromine, and iodine. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 18 Identify the element described by the following: 1. Group 7A, Period 4 A. Br B. Cl C. Mn 2. Group 2A, Period 3 A. beryllium B. boron C. magnesium 3. Group 5A, Period 2 A. phosphorus B. arsenic C. nitrogen Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 19 Identify the element described by the following: 1. Group 7A, Period 4 A. Br 2. Group 2A, Period 3 C. magnesium 3. Group 5A, Period 2 C. nitrogen Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Metals, Nonmetals, and Metalloids 20 The heavy zigzag line separates metals and nonmetals. • Metals are located to the left. • Nonmetals are located to the right. • Metalloids are located along the heavy zigzag line between the metals and nonmetals. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Metals, Nonmetals, and Metalloids and Periodic Table 21 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Properties of Metals, Nonmetals, and Metalloids 22 Metals • are shiny and ductile • are good conductors of heat and electricity Nonmetals • are dull, brittle, and poor conductors • are good insulators Metalloids • are better conductors than nonmetals, but not as good as metals • are used as semiconductors and insulators Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Comparing a Metal, Nonmetal, and Metalloid 23 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 24 Identify each of the following elements as a metal, nonmetal, or metalloid. A. sodium B. chlorine C. silicon D. iron E. carbon Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 25 Identify each of the following elements as metal, nonmetal, or metalloid. A. sodium metal B. chlorine nonmetal C. silicon metalloid D. iron metal E. carbon nonmetal Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 26 List all of the elements that match the description A. Metals in Group 4A Sn, Pb, C, Si, Ge B. Nonmetals in Group 5A As, Sb, Bi, N, P, As, Sb C. Metalloids in Group 4A C, Si, Ge, Sn, Pb Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 27 List all of the elements that match the description A. Metals in Group 4A Sn, Pb B. Nonmetals in Group 5A N, P C. Metalloids in Group 4A Si, Ge Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 3 Atoms and Elements 28 3.3 The Atom Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Dalton's Atomic Theory 29 In Dalton's atomic theory, atoms • are tiny particles of matter • of an element are similar to each other and different • • from other elements of two or more different elements combine to form compounds are rearranged to form new combinations in a chemical reaction Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Subatomic Particles Electrical Charges 30 Atoms contain subatomic particles. • Protons have a positive (+) charge. • Electrons have a negative (– ) charge. • Neutrons are neutral. • Like charges repel and unlike charges attract. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Rutherford's Gold Foil Experiment 31 In Rutherford’s gold foil experiment, positively charged particles • were aimed at atoms of gold • mostly went straight through the atoms • were deflected only occasionally Conclusion: There must be a small, dense, positively charged nucleus in the atom that deflects positive particles that come close. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Rutherford's Gold Foil Experiment 32 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Structure of the Atom 33 An atom consists of • a nucleus that contains protons and neutrons • electrons in a large, empty space around the nucleus Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Mass of the Atom 34 Atomic mass unit • 1 atomic mass unit (amu) has a mass equal to 1/12 of the mass of the carbon-12 atom. • a proton has a mass of about 1 (1.007) amu. • a neutron has a mass of about 1 (1.008) amu. • an electron has a very small mass, 0.000 549 amu. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Subatomic Particles in the Atom 35 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 36 Which of the following subatomic particles fits each of the descriptions below: proton, neutrons, or electrons A. found outside the nucleus B. has a positive charge C. has mass but no charge Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 37 Which of the following subatomic particles fits each of the descriptions below: proton, neutrons, or electrons A. found outside the nucleus B. has a positive charge C. has mass but no charge electrons protons neutrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 3 Atoms and Elements 38 3.4 Atomic Number and Mass Number Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Number 39 The atomic number • is specific for each element • is the same for all atoms of an element • is equal to the number of protons in an atom • appears above the symbol of an element in the Periodic Table Atomic Number Symbol Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition 11 Na Copyright © 2012 by Pearson Education, Inc. Atomic Number = Protons in Atom 40 For example, atomic number = number of protons: • Atomic number H is 1; every H atom has one proton • Atomic number of C is 6; every C atom has six protons • Atomic number of Cu is 29; every Cu atom has 29 protons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Number = Protons in Atom 41 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atoms Are Neutral 42 For neutral atoms, the net charge is zero. number of protons = number of electrons Aluminum has 13 protons and 13 electrons. The net (overall) charge is zero. 13 protons (13+) + 13 electrons (13–) = 0 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 43 Use the periodic table to fill in the atomic number, number of protons, and number of electrons for each of the following elements: Element Atomic Number N Protons Electrons Zn S Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 44 Use the periodic table to fill in the atomic number, number of protons, and number of electrons for each of the following elements: Element Atomic Number N 7 Protons Electrons 7 7 Zn 30 30 30 S 16 16 16 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Mass Number 45 The mass number • represents the number of particles in the nucleus • is equal to the number of protons + the number of neutrons • is always a whole number • does not appear in the periodic table Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Composition of Some Atoms of Different Elements 46 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Study Tips: Protons and Neutrons 47 Number of protons = atomic number Number of protons + neutrons = mass number Number of neutrons = mass number – atomic number Note: Mass number is given for specific isotopes only. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 48 An atom of lead (Pb) has a mass number of 207. A. How many protons are in the nucleus? B. How many neutrons are in the nucleus? C. How many electrons are in the atom? Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 49 An atom of lead (Pb) has a mass number of 207. A. How many protons are in the nucleus? atomic number = 82; number protons = 82 B. How many neutrons are in the nucleus? mass number – number protons = number neutrons 207 – 82 = 125 neutrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 50 An atom of lead (Pb) has a mass number of 207. C. How many electrons are in the atom? An atom is neutral, which means that the number of electrons is equal to the number of protons. An atom of Pb has 82 protons and 82 electrons. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 3 Atoms and Elements 51 3.5 Isotopes and Atomic Mass Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Isotopes 52 Isotopes • are atoms of the same element • have different mass numbers • have same number of protons but different numbers of neutrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Symbols and Subatomic Particles 53 Examples of number of subatomic particles for atoms: Atomic symbol 16 31 O 8 8 p+ 8n 8 e- P 15 15 p+ 16 n 15 e- Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition 65 Zn 30 30 p+ 35 n 30 eCopyright © 2012 by Pearson Education, Inc. Atomic Symbols for Isotopes of Magnesium 54 Mass Numbers 24 12 Mg 25 12 Mg 26 12 Mg Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Symbols for Isotopes of Magnesium 55 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 56 Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the following: Isotope 12C 13C 14C protons neutrons electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 57 Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the following: Isotope 12C 13C 14C protons 6 6 6 neutrons 6 7 8 electrons 6 6 6 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 58 Write the atomic symbols for atoms with the following subatomic particles: A. 8 protons 8 neutrons 8 electrons B. 17 protons 20 neutrons 17 electrons C. 47 protons 60 neutrons 47 electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 59 Write the atomic symbols for atoms with the following subatomic particles: 16 A. 8 protons 8 neutrons 8 electrons O 8 B. 17 protons 20 neutrons 17 electrons C. 47 protons 60 neutrons 47 electrons 37 17 Cl 107 47 Ag Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 60 1. Which of the pairs are isotopes of the same element? 2. In which of the pairs do both atoms have 8 neutrons? 15 A. 8 B. 12 6 C. 15 7 X 15 7 X X 14 6 X X 16 8 X Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 61 1. Which of the pairs are isotopes of the same element? 12 6 B. X 14 6 X 2. In which of the pairs do both atoms have 8 neutrons? C. 15 7 X 16 8 X Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Mass 62 Atomic mass is the • weighted average of all naturally occurring isotopes of that element • number on the periodic table below the chemical symbol with two decimal places Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Calculating Atomic Mass 63 To calculate atomic mass, • use an experimental percent abundance of each isotope of the element • multiply the percent abundance by the atomic mass of that isotope • sum the total mass of each isotope Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Calculating Atomic Mass 64 To calculate atomic mass of Cl, use experimental data for both isotopes of Cl: Isotope atomic mass x % abundance 35Cl 37Cl 34.97 amu x 75.76 = 26.49 amu 100 36.97 amu x 24.24 = 8.962 amu 100 Atomic mass of Cl = 35.45 amu Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. The Atomic Mass of Some Elements 65 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 66 Lithium consists of two naturally occurring isotopes, 6Li and 7Li. Use the periodic table to predict which isotope is the most prevalent one. Periodic table atomic mass of lithium is 6.941 amu. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 67 Lithium consists of two naturally occurring isotopes, 6Li and 7Li. Use the periodic table to predict which isotope is the most prevalent one. Periodic table atomic mass of lithium is 6.941 amu. 6Li and 7Li Since the total atomic mass of 7Li is closer to 7, the mass number of 7Li, the most prevalent isotope is 7Li. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 68 Gallium is an element found in lasers used in compact disc players. In a sample of gallium, there is 60.10% of 69Ga (atomic mass 68.926) atoms and 39.90% of 71Ga (atomic mass 70.925) atoms. What is the atomic mass of gallium? Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 69 69Ga 68.926 amu x 60.10 = 41.42 amu (from 69Ga) 100 71Ga 70.925 amu x 39.90 = 28.30 amu (from 71Ga) 100 Atomic mass Ga = 69.72 amu 31 Ga 69.72 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 3 Atoms and Elements 70 3.5 Isotopes and Atomic Mass Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Isotopes 71 Isotopes • are atoms of the same element • have different mass numbers • have same number of protons but different numbers of neutrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Symbols and Subatomic Particles 72 Examples of number of subatomic particles for atoms: Atomic symbol 16 31 O 8 8 p+ 8n 8 e- P 15 15 p+ 16 n 15 e- Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition 65 Zn 30 30 p+ 35 n 30 eCopyright © 2012 by Pearson Education, Inc. Atomic Symbols for Isotopes of Magnesium 73 Mass Numbers 24 12 Mg 25 12 Mg 26 12 Mg Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Symbols for Isotopes of Magnesium 74 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 75 Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the following: Isotope 12C 13C 14C protons neutrons electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 76 Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the following: Isotope 12C 13C 14C protons 6 6 6 neutrons 6 7 8 electrons 6 6 6 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 77 Write the atomic symbols for atoms with the following subatomic particles: A. 8 protons 8 neutrons 8 electrons B. 17 protons 20 neutrons 17 electrons C. 47 protons 60 neutrons 47 electrons Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 78 Write the atomic symbols for atoms with the following subatomic particles: 16 A. 8 protons 8 neutrons 8 electrons O 8 B. 17 protons 20 neutrons 17 electrons C. 47 protons 60 neutrons 47 electrons 37 17 Cl 107 47 Ag Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 79 1. Which of the pairs are isotopes of the same element? 2. In which of the pairs do both atoms have 8 neutrons? 15 A. 8 B. 12 6 C. 15 7 X 15 7 X X 14 6 X X 16 8 X Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 80 1. Which of the pairs are isotopes of the same element? 12 6 B. X 14 6 X 2. In which of the pairs do both atoms have 8 neutrons? C. 15 7 X 16 8 X Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Mass 81 Atomic mass is the • weighted average of all naturally occurring isotopes of that element • number on the periodic table below the chemical symbol with two decimal places Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Calculating Atomic Mass 82 To calculate atomic mass, • use an experimental percent abundance of each isotope of the element • multiply the percent abundance by the atomic mass of that isotope • sum the total mass of each isotope Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Calculating Atomic Mass 83 To calculate atomic mass of Cl, use experimental data for both isotopes of Cl: Isotope atomic mass x % abundance 35Cl 37Cl 34.97 amu x 75.76 = 26.49 amu 100 36.97 amu x 24.24 = 8.962 amu 100 Atomic mass of Cl = 35.45 amu Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. The Atomic Mass of Some Elements 84 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 85 Lithium consists of two naturally occurring isotopes, 6Li and 7Li. Use the periodic table to predict which isotope is the most prevalent one. Periodic table atomic mass of lithium is 6.941 amu. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 86 Lithium consists of two naturally occurring isotopes, 6Li and 7Li. Use the periodic table to predict which isotope is the most prevalent one. Periodic table atomic mass of lithium is 6.941 amu. 6Li and 7Li Since the total atomic mass of 7Li is closer to 7, the mass number of 7Li, the most prevalent isotope is 7Li. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 87 Gallium is an element found in lasers used in compact disc players. In a sample of gallium, there is 60.10% of 69Ga (atomic mass 68.926) atoms and 39.90% of 71Ga (atomic mass 70.925) atoms. What is the atomic mass of gallium? Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 88 69Ga 68.926 amu x 60.10 = 41.42 amu (from 69Ga) 100 71Ga 70.925 amu x 39.90 = 28.30 amu (from 71Ga) 100 Atomic mass Ga = 69.72 amu 31 Ga 69.72 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 3 Atoms and Elements 89 3.6 Electron Energy Levels Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electromagnetic Spectrum 90 The electromagnetic spectrum shows the arrangement of wavelengths of electromagnetic radiation, with the visible range from 700 to 400 nm. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Elements Have a Unique Atomic Spectrum 91 When light from an element that is heated passes through a prism, it separates into a unique set of distinct lines of color called an atomic spectrum. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Energy Levels 92 Energy levels • are assigned numbers n = 1, 2, 3, 4, and so on • increase in energy as the value of n increases • are like the rungs of a ladder, with the lower energy levels nearer the nucleus Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Energy Levels 93 Energy levels have a maximum number of electrons equal to 2n2. Energy level n=1 n=2 n=3 Maximum number of electrons 2(1)2 = 2(1) = 2 2(2)2 = 2(4) = 8 2(3)2 = 2(9) = 18 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Changes in Electron Energy Level 94 • Electrons move to a higher energy level when it absorbs energy. • When electrons fall back to a lower energy level, light is emitted. • The energy emitted or absorbed is equal to the differences between the two energy levels. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Changes in Electron Energy Level 95 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 1 96 Period 1 H 1 electron in 1st energy level. He 2 electrons in 1st energy level. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 2 97 Period 2 Energy Level Li Be B C N O F Ne 1st 2 2 2 2 2 2 2 2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition 2nd 1 2 3 4 5 6 7 8 Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 3 98 Period 3 Energy Level Na Mg Al Si P S Cl Ar 1st 2 2 2 2 2 2 2 2 2nd 8 8 8 8 8 8 8 8 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition 3rd 1 2 3 4 5 6 7 8 Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 4 99 Period 4 Energy Level 1st 2nd 3rd 4th K Ca 2 2 8 8 8 8 1 2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Arrangements Beyond 20 100 Energy Level 1st 2nd 3rd 4th 5th 6th 7th Number of Electrons 8 18 32 32 18 8 2 Electron arrangements are written as: O = 2,6 P = 2,8,5 Ca = 2,8,8,2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 101 Write the electron arrangement for the following elements: C Si O N Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 102 Write the electron arrangement for the following elements: C = 2,4 Si = 2,8,4 O = 2,6 N = 2,5 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 3 Atoms and Elements 103 3.6 Electron Energy Levels Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electromagnetic Spectrum 104 The electromagnetic spectrum shows the arrangement of wavelengths of electromagnetic radiation, with the visible range from 700 to 400 nm. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Elements Have a Unique Atomic Spectrum 105 When light from an element that is heated passes through a prism, it separates into a unique set of distinct lines of color called an atomic spectrum. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Energy Levels 106 Energy levels • are assigned numbers n = 1, 2, 3, 4, and so on • increase in energy as the value of n increases • are like the rungs of a ladder, with the lower energy levels nearer the nucleus Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Energy Levels 107 Energy levels have a maximum number of electrons equal to 2n2. Energy level n=1 n=2 n=3 Maximum number of electrons 2(1)2 = 2(1) = 2 2(2)2 = 2(4) = 8 2(3)2 = 2(9) = 18 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Changes in Electron Energy Level 108 • Electrons move to a higher energy level when it absorbs energy. • When electrons fall back to a lower energy level, light is emitted. • The energy emitted or absorbed is equal to the differences between the two energy levels. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Changes in Electron Energy Level 109 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 1 110 Period 1 H 1 electron in 1st energy level. He 2 electrons in 1st energy level. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 2 111 Period 2 Energy Level Li Be B C N O F Ne 1st 2 2 2 2 2 2 2 2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition 2nd 1 2 3 4 5 6 7 8 Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 3 112 Period 3 Energy Level Na Mg Al Si P S Cl Ar 1st 2 2 2 2 2 2 2 2 2nd 8 8 8 8 8 8 8 8 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition 3rd 1 2 3 4 5 6 7 8 Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 4 113 Period 4 Energy Level 1st 2nd 3rd 4th K Ca 2 2 8 8 8 8 1 2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Arrangements Beyond 20 114 Energy Level 1st 2nd 3rd 4th 5th 6th 7th Number of Electrons 8 18 32 32 18 8 2 Electron arrangements are written as: O = 2,6 P = 2,8,5 Ca = 2,8,8,2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 115 Write the electron arrangement for the following elements: C Si O N Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 116 Write the electron arrangement for the following elements: C = 2,4 Si = 2,8,4 O = 2,6 N = 2,5 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 3 Atoms and Elements 117 3.6 Electron Energy Levels Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electromagnetic Spectrum 118 The electromagnetic spectrum shows the arrangement of wavelengths of electromagnetic radiation, with the visible range from 700 to 400 nm. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Elements Have a Unique Atomic Spectrum 119 When light from an element that is heated passes through a prism, it separates into a unique set of distinct lines of color called an atomic spectrum. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Energy Levels 120 Energy levels • are assigned numbers n = 1, 2, 3, 4, and so on • increase in energy as the value of n increases • are like the rungs of a ladder, with the lower energy levels nearer the nucleus Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Energy Levels 121 Energy levels have a maximum number of electrons equal to 2n2. Energy level n=1 n=2 n=3 Maximum number of electrons 2(1)2 = 2(1) = 2 2(2)2 = 2(4) = 8 2(3)2 = 2(9) = 18 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Changes in Electron Energy Level 122 • Electrons move to a higher energy level when it absorbs energy. • When electrons fall back to a lower energy level, light is emitted. • The energy emitted or absorbed is equal to the differences between the two energy levels. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Changes in Electron Energy Level 123 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 1 124 Period 1 H 1 electron in 1st energy level. He 2 electrons in 1st energy level. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 2 125 Period 2 Energy Level Li Be B C N O F Ne 1st 2 2 2 2 2 2 2 2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition 2nd 1 2 3 4 5 6 7 8 Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 3 126 Period 3 Energy Level Na Mg Al Si P S Cl Ar 1st 2 2 2 2 2 2 2 2 2nd 8 8 8 8 8 8 8 8 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition 3rd 1 2 3 4 5 6 7 8 Copyright © 2012 by Pearson Education, Inc. Electron Arrangements in Period 4 127 Period 4 Energy Level 1st 2nd 3rd 4th K Ca 2 2 8 8 8 8 1 2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron Arrangements Beyond 20 128 Energy Level 1st 2nd 3rd 4th 5th 6th 7th Number of Electrons 8 18 32 32 18 8 2 Electron arrangements are written as: O = 2,6 P = 2,8,5 Ca = 2,8,8,2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 129 Write the electron arrangement for the following elements: C Si O N Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 130 Write the electron arrangement for the following elements: C = 2,4 Si = 2,8,4 O = 2,6 N = 2,5 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 3 Atoms and Elements 131 3.7 Trends in Periodic Properties Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Group Number and Valence Electrons 132 For representative elements in Groups 1A–8A, chemical properties are due to the number of valence electrons. Valence electrons are the number of electrons in the outermost energy level. The group number gives the number of valence electrons for the representative elements. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Group Number and Valence Electrons 133 Group Number 1A 2A 3A 4A 5A 6A 7A 8A # Valence Electrons 1 2 3 4 5 6 7 8 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron-Dot Symbols 134 Electron-dot symbols • are also known as Lewis structures • represent the valence electrons as dots placed on sides of symbol For example, Al = 2,8,3 Three valence electrons are represented as dots: Al Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron-Dot Symbol for Mg 135 Possible electron-dot symbols for magnesium, with the electron arrangement of 2,8,2, • include 2 valence electrons, represented as dots • can be drawn in more than one way Mg Mg Mg Mg Mg Mg Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron-Dot Symbol for Mg 136 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Electron-Dot Symbols for Selected Elements 137 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 138 Write the electron-dot symbol for each of the following elements: Cl, C, N. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 139 Write the electron-dot symbol for each of the following elements: Cl C N Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Size 140 Atomic size • is determined by the atom’s atomic radius, the distance between nucleus and outermost electrons • increases for representative elements from top to bottom of the periodic table • decreases within a period due to increased number of protons in nucleus Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Size 141 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Atomic Size 142 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Ionization Energy 143 Ionization energy • is the energy required to remove one of the outermost electrons from an atom Na(g) + energy (ionization) Na+(g) + e− • decreases down a group, increases across a period from left to right Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Ionization Energy 144 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Metallic Character 145 An element with metallic character is one that loses electrons easily. Metallic character • is more prevalent in metals on left side of periodic table • is less for nonmetals on right side of periodic table that do not lose electrons easily Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Metallic Character 146 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Summary of Trends in Periodic Table 147 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 148 Given the following elements: C N Cl Which is the largest atom? Which has the highest ionization energy? Which belongs to Group 5A? Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 149 Given the following elements: C Which is the largest atom? Which has the highest ionization energy? Which belongs to Group 5A? Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition N Cl C Cl N Copyright © 2012 by Pearson Education, Inc.