CHAPTER 3 ELEMENTS AND THE PERIODIC TABLE SECTION
CHAPTER 3: ELEMENTS AND THE PERIODIC TABLE SECTION 2: ORGANIZING THE ELEMENTS
PATTERNS IN THE ELEMENTS • Dmitri Mendeleev (19 th century) noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass. • Atomic mass: average mass of all the isotopes of that element • Mendeleev found that the properties of elements repeated like the days of the week on a calendar. • Predicted that the blank spaces in his periodic table would be filled by elements that had not yet been discovered. He even predicted the properties of those elements.
MENDELEEV’S PERIODIC TABLE
CHECKPOINT 1 • What is atomic mass?
CHECKPOINT 1 • What is atomic mass? • Average mass of all the isotopes of that element
THE MODERN PERIODIC TABLE • Periodic table: a chart of the elements showing the repeating pattern of their properties • Periodic means “in a regular, repeated pattern” • A period is a row (horizontal) • Arranged by atomic number instead of atomic mass (Henry Mosely)
FINDING DATA ON ELEMENTS • Atomic Number (number of protons) • Chemical Symbols and Names • Chemical symbol: a one- or two-letter representation of an element • Average Atomic Mass (weighted average of the mass of all of the isotopes of an element)
CHECKPOINT 2 • What is the difference between the way that Mendeleev arranged the periodic table and how the modern periodic table is arranged?
CHECKPOINT 2 • What is the difference between the way that Mendeleev arranged the periodic table and how the modern periodic table is arranged? • Mendeleev arranged the elements by their atomic mass. The modern periodic table is arranged by increasing atomic number.
CALCULATING AVERAGE ATOMIC MASS
ORGANIZATION OF THE PERIODIC TABLE • The properties of an element can be predicted from its location in the periodic table. • Period: horizontal rows on the periodic table • As you move across a period from left to right, properties of the elements change according to a pattern • Group: vertical columns on the periodic table • a. k. a. family • Numbered from 1 -18 • Elements in each group have similar characteristics • Arranged like a calendar
CHECKPOINT 3 • What is the difference between a period and a group?
CHECKPOINT 3 • What is the difference between a period and a group? • A period is a horizontal row and a group is a vertical column.
POST-LESSON QUIZ 1. What does it mean for something to be “periodic”? a. it increases b. it decreases c. it has a regular repeating pattern d. it is random
POST-LESSON QUIZ 2. Who developed the first periodic table? a. Henry Moseley b. Dmitri Mendeleev c. Robert Boyle d. Gregor Mendel
POST-LESSON QUIZ 3. What is the average mass of all the isotopes of an element? a. atomic mass b. atomic number c. chemical symbol d. electron configuration
POST-LESSON QUIZ 4. What is a vertical column on the periodic table called? a. line b. period c. class d. group
POST-LESSON QUIZ 5. What is a horizontal row on the periodic table called? a. line b. period c. class d. group
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