Chapter 5

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# Chapter 5 - PowerPoint PPT Presentation

Chapter 5. The Periodic Table. 5-1 Organizing the Elements. What does the word “ periodic ” mean? Periodic : recurring at regular intervals Periodic table – is an arrangement of elements in columns based on a set of properties that repeat from row to row. Mendeleev 1869.

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### Chapter 5

The Periodic Table

5-1 Organizing the Elements
• What does the word “periodic” mean?
• Periodic: recurring at regular intervals
• Periodic table – is an arrangement of elements in columns based on a set of properties that repeat from row to row
Mendeleev 1869
• See Figure 3 on page 127
• Arranged elements according to increasing atomic mass in rows
• Put elements of similar properties in the same column
• Left blank spots in table which predicted properties of elements not yet discovered
Evidence Supporting Mendeleev’s Table
• Named eka-aluminum to the element that belonged one space below aluminum on the table
• 1875- French chemist discovered a new element and named it gallium (Ga)
• Gallium is a soft metal used in traffic signals
Similarity of the two
• Eka-aluminum and Gallium were similar in properties, so they were determined to be the same
• The close match between Mendeleev’s prediction and the actual properties of new elements showed how useful his periodic table could be
Questions
• Which of the following is a symbol for an element?
• Aluminum
• Al
• al
• AL
Questions

3. What happens to the composition of matter during a physical change? Does it change or remain the same?

Questions

2. Is flammability a physical property or a chemical property?

Questions

4. What does the atomic number of an element represent?

Question

5. Isotopes of element have different numbers of

• Neutrons
• Electrons
• Protons
• nuclei
Question

6. True or False : Electrons in atoms occupy orbitals in energy levels

5-2 The Modern Periodic Table
• Mendeleev developed the periodic table before the discovery of protons.
• In the modern periodic table, elements are arranged by increasing atomic number
Periods
• Each row in the table of elements is called a period
• Period 1 has two elements
• Periods 2 and 3 have 8 elements
• Periods 4 and 5 have 18 elements
• Period 6 has 32 elements
• There are 7 periods total on the periodic table
• The number of electrons per period varies because of the number of available orbitals increases from energy level to energy level
Groups
• Each column on the periodic table is called a group
• The elements within a group have similar properties
• Properties of elements repeat in a predicable way when atomic number are used to arrange elements into groups
• The pattern of repeating properties is the periodic law
• There are 18 groups on the periodic table
Atomic Mass
• Atomic mass is a value that depends on the distribution of an element’s isotopes in nature and the masses of those isotopes
• An atomic mass unit (amu) is defined as one twelfth the mass of carbon-12 atom
Average Atomic Mass
• Weighted average of the atomic masses of the naturally occurring isotopes of an element
Weighted Averages
• Average Atomic Mass =
• (isotope mass)(relative abundance[dec]) + (isotope mass)(relative abundance[dec])
• (0.75771)(34.96885amu) + (0.24229)(36.96590amu)
• = 35.453 amu
ISOTOPES
• Atoms of the same element that differ in mass
• Have the same # protons but different # neutrons
Classes of Elements
• Elements are classified as metals, nonmetals, and metalloids
• Metal:
• Good conductor of heat & electricity
• Ductile –able to be drawn into a fine wire
• Malleability – can be hammered or rolled into thin sheets
• Nonmetal
• Poor conductor of heat & electricity
• Brittle
• Metalloids
• Some characteristics of metals & nonmetals
Beaker Breaker
• Isotopes have the same # of _______ but different #of __________
• What is the name of group 1 on the periodic table?
• How many periods are there on the periodic table?
Transition Metals
• Transition metals are elements that form a bridge between the elements on the left and right sides of the table
The Lanthanides
• The 14 elements with atomic numbers from 58(cerium, Ce) to 71(lutetium, Lr)
• Similar in chemical and physical properties
The Actinides
• The 14 elements with atomic number from 90(thorium, Th) to 103(lawrencium, Lr)
Variation across a period
• Across a period from left to right, the elements become less metallic and more nonmetallic in their properties
• Most reactive metals are on the left side of the table
• Most reactive nonmetals are on the right in Group 17
5-3 Representative Groups
• Valence electron – is an electron that is in the highest occupied energy level of an atom
• Elements in a group have similar properties because they have the same number of valence electrons
• Valence electrons explain the location of hydrogen, hydrogen has a single electron
Alkali Metals
• Elements in Group 1A are called alkali metals.
• Single valence electron and are extremely reactive
• The reactivity of alkali metals increases from the top of Group 1A to the bottom
The Alkaline Earth Metals
• The elements in Group 2A are called alkaline earth metals
• All alkaline earth metals have two valence electrons
• They are harder than group 1A
• Differences in reactivity among the alkaline earth metals are shown by the ways they react with water
• Calcium, strontium and barium react easily with cold water
• Magnesium will react with hot water. No change appears to occur when beryllium is added to water
The Boron Family
• Group 3A contains the metalloid boron.
• Aluminum is the most abundant metal in the Earth’s crust
• Glass that contains boron is used to make laboratory glassware such as flasks
The Carbon Family
• Group 4A contains nonmetal carbon
• Two metalloids – silicon and germanium
• Two metals – lead and tin
• Except for water, most of the compounds in your body contains carbon
• Silicon is the second most abundant element in the Earth’s crust
The Nitrogen Family
• Group 5A contains two nonmetals – nitrogen and phosphorus
• Two metalloids – arsenic and antimony
• One metal –bismuth
• Besides nitrogen, fertilizers often contain phosphorus
The Oxygen Family
• Group 6A has three nonmetals – oxygen, sulfur, and selenium
• Two metalloids – tellurium and polonium
• All have 6 valence electrons
• Oxygen is the most abundant element in the Earth’s crust
The Halogens
• The elements in Group 7A are called halogens
• They have seven valence electrons
• Despite their physical differences, the halogens have similar chemical properties
• They are highly reactive nonmetals
• Fluorine is the most reactive
The Noble Gases
• The elements in Group 8A are called the noble gases
• Helium has 2 valence electrons
• All other noble gases have 8 valence electrons
• The noble gases are colorless and odorless and extremely unreactive
• All the noble gases except radon are used in “neon” lights