Slide 1

Section 2 The Modern Periodic Table The Elements Slide 2 Key Concepts How is the modern periodic table organized? What does the atomic mass of an element depend on? What categories are used to classify elements on the periodic table? How do properties vary across a period in the periodic table? Slide 3 Middle C D E F G A B C D E F G G A B C D E F G A B On this synthesizer keyboard, there is a repeating pattern of notes. The eight-note interval between any two notes with the same name is an octave. Observing How many octaves are visible on the keyboard? Slide 4 The Periodic Law Mendeleev developed his periodic table before the discovery of protons. Henry Moseley Slide 5 The Periodic Law Henry Moseley Protons were discovered in 1911 by Rutherford (Atomic Number) Moseley used Atomic number to arrange the elements All of the elements with similar properties fell into place. Slide 6 The Periodic Law Slide 7 Henry Moseleys Periodic Table: The Modern Periodic Table Slide 8 The Periodic Law In the modern periodic table, elements are arranged by increasing atomic number (number of protons). States that the physical and chemical properties of the elements are periodic functions of their atomic number. Slide 9 The Periodic Law Periods Each row in the table of elements is a period. Period 1 has 2 elements. Periods 2 and 3 have 8 elements. Periods 4 and 5 have 18 elements. Period 6 has 32 elements. Elements within a period are not similar in properties Slide 10 The Periodic Law Groups or Families Each column on the periodic table is called a group or family. The elements within a group have similar properties. The elements in a group have similar electron configurations. An elements electron configuration determines its chemical properties This pattern of repeating properties is the periodic law. Slide 11 Atomic Mass Atomic mass is a value that depends on the distribution of an elements isotopes in nature and the masses of those isotopes. The Elements Slide 12 Element Key Cl Chemical Symbol 17 Atomic Number Chlorine 35.453 Atomic Mass This box provides four pieces of information about the element chlorine: its symbol, its name, its atomic number, and its atomic mass. Slide 13 Atomic Mass Weighted Averages 34.969amu x 0.7578 = 26.499amu 36.966amu x 0.2422 = 8.954amu 26.499amu + 8.954amu 35.453amu Appears on the Periodic Table Slide 14 Classes of Elements Elements are classified as metals, nonmetals, and metalloids. Slide 15 Classes of Elements Metals Elements that are good conductors of electric current and heat. Most metals are malleable and ductile. Some metals are extremely reactive and some do not react easily. Except for mercury, metals are solids at room temperature. Found to the left of the staircase on the Periodic Table Slide 16 Metals Slide 17 Classes of Elements Nonmetals Elements that are poor conductors of heat and electric current. Tend to be brittle Some nonmetals are extremely reactive, some hardly react at all, and some fall somewhere in between. Found to the right of the staircase on the Periodic Table Slide 18 Nonmetals Slide 19 Classes of Elements Metalloids Elements with properties that fall between those of metals and nonmetals. A metalloids ability to conduct electric current varies with temperature. Pure silicon (Si) and germanium (Ge) are good insulators at low temperatures and good conductors at high temperatures. Found on the staircase on the Periodic Table. Slide 20 Metalloids Slide 21 Variation Across a Period Across a period from left to right, the elements become less metallic and more nonmetallic in their properties. The properties within a period change in a similar way from left to right across the table Sodium Magnesium Aluminum Silicon Phosphorus Sulfur Chlorine Argon Slide 22 Reviewing Concepts 1. What determines the order of the elements in the modern periodic table? 2. Describe the periodic law. 3. What two factors determine the atomic mass of an element? 4. Name three categories that are used to classify the elements in the periodic table. 5. What major change occurs as you move from left to right across the periodic table?