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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.

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chapter 5

Chapter 5

The Periodic Table

5 1 organizing the elements
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
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
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
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
  • Which of the following is a symbol for an element?
  • Aluminum
  • Al
  • al
  • AL

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


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


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


5. Isotopes of element have different numbers of

  • Neutrons
  • Electrons
  • Protons
  • nuclei

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

5 2 the modern periodic table
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
  • 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
  • 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
  • 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
Average Atomic Mass
  • Weighted average of the atomic masses of the naturally occurring isotopes of an element
weighted averages
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
  • Atoms of the same element that differ in mass
  • Have the same # protons but different # neutrons
classes of elements
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
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
  • Transition metals are elements that form a bridge between the elements on the left and right sides of the table
the lanthanides
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 Actinides
  • The 14 elements with atomic number from 90(thorium, Th) to 103(lawrencium, Lr)
variation across a period
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
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
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 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
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
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
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
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 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 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