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REVIEW FROM CHAPTER 4 n Atomic Number = n Number of Electrons = n Mass Number = 2/25/14 Chapter 5: The Periodic Table 1 REVIEW FROM CHAPTER 4 n Atomic Number = # of Protons n Number of Electrons = # of Protons n Mass Number = Neutrons + Protons n Mass Number = Neutrons + Atomic # 2/25/14 Chapter 5: The Periodic Table 2 REVIEW FROM CHAPTER 4 n # of Protons = Atomic # n # of Electrons = # of Protons = Atomic # n # of Neutrons = Mass # - Atomic # 2/25/14 Chapter 5: The Periodic Table 3 5.2 THE MODERN PERIODIC TABLE n Vocabulary: period, group, periodic law, atomic mass unit (amu), metals, transition metals, nonmetals n Objectives: n Describe the arrangement of elements in the modern periodic table. n Explain how the atomic mass of an element is determined and how atomic mass units are defined. n Identify general properties of metals, nonmetals, and metalloids. n Describe how properties of elements change across a period in the periodic table. 2/25/14 Chapter 5: The Periodic Table 4 THE PERIODIC LAW n Mendeleev developed periodic table before discovery of protons. n Modern periodic table, elements are arranged by increasing atomic number. Uses of modern periodic table of elements: classify elements & compare properties n 2/25/14 Chapter 5: The Periodic Table 5 MODERN PERIODIC TABLE OF ELEMENTS 2/25/14 Chapter 5: The Periodic Table 6 PERIODS THE PERIODIC LAW: PERIODS period - each row on periodic table of elements 2/25/14 Chapter 5: The Periodic Table 7 CHAPTER 4 REVIEW: ENERGY LEVELS & ORBITALS n Energy levels - possible energies that electrons in an atom can have n Orbital - region of space around nucleus where an electron is likely to be found n Each orbital can contain 2 electrons at most. 2/25/14 Chapter 5: The Periodic Table 8 THE PERIODIC LAW: PERIODS n # of elements per period varies because # of available orbitals increases from energy level to energy level. n To understand structure of table, think about what happens as atomic number increases. n atomic number = # of protons n How does this relate to # of electrons in an atom? 2/25/14 Chapter 5: The Periodic Table 9 THE PERIODIC LAW: PERIODS n 1st energy level has only 1 orbital (therefore, only holds 2 electrons). n Hydrogen (H) & Helium (He) can fit in this energy level. n Hydrogen (H) atom 1 electron. n Hydrogen (H) Helium (He) atom 2 electrons Helium (He) 2/25/14 Chapter 5: The Periodic Table 10 THE PERIODIC LAW: PERIODS n Lithium (Li) n 3 electrons. n 1 of 3 electrons must be in 2nd energy level n 1st element in Period 2. n Sodium (Na) n 11 electrons. n 1 electron in its 3rd energy level. n 1st element in Period 3. Link: http://web.visionlearning.com/custom/chemistry/animations/CHE1.3-an-atoms.shtml 2/25/14 Chapter 5: The Periodic Table 11 THE PERIODIC LAW: PERIODS n This pattern applies to all elements in first column of table. 1. Hydrogen (H) 2. Lithium (Li) 3. Sodium (Na) 4. Potassium (K) 5. Rubidium (Rb) 6. Cesium (Cs) 7. Francium (Fr) 2/25/14 Chapter 5: The Periodic Table 12 THE PERIODIC LAW: PERIODS n 2/25/14 The elements that start off each row on the Periodic Table (H, Li, Na, K Rb, Cs and Fr) also start off each of the seven main energy levels. Chapter 5: The Periodic Table 13 THE PERIODIC LAW: PERIODS n 2/25/14 Elements that start off each row also start off each of the 7 main energy levels. Chapter 5: The Periodic Table 14 THE PERIODIC LAW: GROUPS GROUPS group - each column on periodic table of elements 2/25/14 Chapter 5: The Periodic Table 15 THE PERIODIC LAW: GROUPS n Elements within a group have similar electron configurations & therefore similar chemical properties. n Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups. n Periodic law - pattern of repeating properties 2/25/14 Chapter 5: The Periodic Table 16 ATOMIC MASS There are 4 pieces of information for each element. 17 Symbol Cl Chlorine Atomic Mass 2/25/14 35.453 Chapter 5: The Periodic Table Atomic Number Name of the element 17 ATOMIC MASS n Atomic mass is a value that depends on 1. distribution of an element s isotopes in nature 2. masses of those isotopes 17 Cl Chlorine Atomic Mass 2/25/14 35.453 Chapter 5: The Periodic Table 18 ATOMIC MASS: ATOMIC MASS UNITS n 1 isotope is chosen to serve as standard for element. n Scientists assigned 12 atomic mass units to carbon-12 atom (6 protons + 6 neutrons). n atomic mass unit (amu) - one twelfth the mass of a carbon-12 atom. 2/25/14 Chapter 5: The Periodic Table 19 ATOMIC MASS: ISOTOPES OF CHLORINE n In nature, most elements exists as a mixture of 2 or more isotopes. n 2 natural isotopes of chlorine: n Chlorine-35 (17 protons + 18 neutrons) n Chlorine-37 (17 protons + 20 neutrons) Unit understood to be in amu 2/25/14 Chapter 5: The Periodic Table 17 Cl Chlorine 35.453 20 ATOMIC MASS: WEIGHTED AVERAGES Weighted Averages to Determine Grade n Tests…………………………………………………………. 25 % n Labs…………………………………….…...…………......... 20 % n Quizzes (and Do Now) ………………………………….... 15 % n Homework ………………………………………………….. 15 % n Class Participation…………………….……..…………….. 10 % n Binder Checks ……………………………………………... 05 % n Other ……………………………………….……................ 10 % 2/25/14 Chapter 5: The Periodic Table 21 ATOMIC MASS: WEIGHTED AVERAGES n 2 natural isotopes of chlorine: n Chlorine-35 n Chlorine-37 n If you find the average of these 2 ((35+37)/2) it would equal 35.967, not 35.453. n 2/25/14 The atomic mass value of Cl in the periodic table is a weighted average. Chapter 5: The Periodic Table 17 Cl Chlorine 35.453 22 ISOTOPES OF CHLORINE 2/25/14 Chapter 5: The Periodic Table 23 THE MODERN PERIODIC TABLE OF ELEMENTS (FROM TEXTBOOK) Presents different ways to classify elements. 2/25/14 Chapter 5: The Periodic Table 24 CLASSES OF ELEMENTS 1. solids, liquids, or gases based on their states of matter at room temperature (23°C). 2/25/14 Gases Solids Liquids 1 6 80 H C Hg Hydrogen 1.079 Carbon 12.011 Mercury 200.59 Chapter 5: The Periodic Table 25 CLASSES OF ELEMENTS 2. Elements divided into those that occur naturally & those that do not. 2/25/14 n Atomic #s 1-92 occur on Earth (except Tc & Pm). n Atomic #s 93 & higher do not occur naturally. Chapter 5: The Periodic Table 26 CLASSES OF ELEMENTS 3. Elements placed into categories based on their general properties 2/25/14 Elements are classified as n Metals (Left) n Nonmetals (Right) n Metalloids (Middle) Chapter 5: The Periodic Table 27 CLASSES OF ELEMENTS: METALS (Blue Boxes) n Metals - elements that are good conductors of electric current & heat. n Majority of elements n Most/many metals are n n n n 2/25/14 solids at room temperature (except Hg) malleable ductile (can be drawn into thin wires) Some extremely reactive, some do not react easily. n i.e. Gold (Au) remains shiny (doesn t react w/ O) but magnesium (Mg) quickly dulls (reacts w/ O). Chapter 5: The Periodic Table 28 CLASSES OF ELEMENTS: METALS – TRANSITION METALS n Transition metals are elements that form a bridge between elements on left & right sides of table. Groups 3-12. n Examples: Cu & Ag. n 1 property of transition metals: n Ability to form compounds with distinctive colors. n i.e. compound of erbium & oxygen used to tint lenses. 2/25/14 Chapter 5: The Periodic Table 29 CLASSES OF ELEMENTS: NONMETALS (Yellow Boxes) n Nonmetals - elements that are poor conductors of heat & electric current n Examples: He, C, Cl, S n Low boiling points à many gases at room temperature. i.e. N & O n Solid at room temperature tend to be brittle. n Vary in chemical and physical properties. n i.e. reactive (fluorine) to not reactive 2/25/14 Chapter 5: The Periodic Table 30 CLASSES OF ELEMENTS: METALLOIDS (Green Boxes) n Metalloids - elements with properties that fall between those of metals and nonmetals. Metals Good Conductors of Electric Current n 2/25/14 Metalloids Varies with temperature Nonmetals Poor Conductors of Electric Current Examples: Pure silicon (Si) & Germanium (Ga) are good insulators at low temperatures & good conductors at high temperatures. Chapter 5: The Periodic Table 31 VARIATION ACROSS A PERIOD n 2/25/14 Across a period from left to right, the elements become less metallic & more nonmetallic in their properties. Chapter 5: The Periodic Table 32 REVIEW n Name & describe 3 categories that are used to classify the elements in the periodic table (based on their general properties). n Which type of metals tend to form compounds with distinctive colors? 2/25/14 Chapter 5: The Periodic Table 33 REVIEW n Name & describe 3 categories that are used to classify the elements in the periodic table (based on their general properties). n n n n Which type of metals tend to form compounds with distinctive colors? n 2/25/14 Metals Nonmetals Metalloids Transition metals Chapter 5: The Periodic Table 34 2/25/14 Chapter 5: The Periodic Table 35 LINKS n David s Wizzy Periodic Table - Click on Element to See Atom Structure. http://www.colorado.edu/physics/2000/applets/a2.html n Interactive Periodic Table of Elements. http://www.webelements.com/ http://www.chemicool.com/ http://web.visionlearning.com/ custom/chemistry/custom/CHE1.4-pg-table.shtml 2/25/14 Chapter 5: The Periodic Table 36