Mendeleev and Chemical Periodicity 

• Mendeleev noticed that when the elements were arranged in order of increasing atomic mass, certain similarities in their chemical properties appeared at regular intervals.

  
  

  •Repeating patterns are referred to as periodic.

  
  

  •Mendeleev created a table in which elements with similar properties were grouped together—a periodic table of the elements.

Mendeleev and Chemical Periodicity 

• After Mendeleev placed all the known elements in his periodic table, several empty spaces were left.

  
  

  •In 1871 Mendeleev predicted the existence and properties of elements that would fill three of the spaces.

  
  

  •By 1886, all three of these elements had

  been discovered.

Moseley and the Periodic Law 

• In 1911, the English scientist Henry Moseley discovered that the elements fit into patterns better when they were arranged according to atomic number, rather than atomic weight.

  
  

  •The Periodic Law states that the physical and chemical properties of the elements are periodic functions of their atomic numbers.

The Modern Periodic Table 

The Periodic Table is an arrangement of the elements in order of their atomic numbers so that elements with similar properties fall in the same column, or group.

Three classes of elements are metals, nonmetals, and metalloids.

Metals, nonmetals, and metalloids.

• Metals are generally malleable, ductile, and good conductors of heat and electric current.

• Most nonmetals are brittle, poor conductors of heat and electric current. Many are gases at room temp.

• A metalloid generally has properties that are similar to those of metals and nonmetals.

Info on the PT

• The periodic table usually displays the symbols and names of the elements, along with information about the structure of their atoms.

• Black letters are solid elements, red letters are gases, blue letters are liquids and white or gray letters are not found in nature.

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Periods and Blocks of the Periodic Table 

The periodic table is divided into four blocks, the s, p, d, and f blocks. The name of each block is determined by the electron sublevel being filled in that block

Groups of the Periodic Table

• The elements of Group 1 of the periodic table are known as the alkali metals. 

• lithium, sodium, potassium, rubidium, cesium, and francium

• In their pure state, all of the alkali metals have a silvery appearance and are soft enough to cut with a knife.

• They are highly reactive

• 1 valence electron

Groups of the Periodic Table

• The elements of Group 2 of the periodic table are called the alkaline-earth metals.

• beryllium, magnesium, calcium, strontium, barium, and radium

• Group 2 metals are less reactive than the alkali metals, but are still too reactive to be found in nature in pure form.

• 2 valence electrons

Groups of the Periodic Table

• The elements of Group 3-12 of the periodic table are called the transition metals.

• copper, iron, gold, titanium, iron, etc.

• Transition metals are shiny, good conductors of electricity, are less reactive than alkali metals and have high melting points

Groups of the Periodic Table

• The elements of Group 17 of the periodic table are called the halogens.

• Fluorine, Chlorine, Bromine, Iodine, & Astatine.

• Halogens can be gaseous, liquid, or solid at room temperature.

• Halogens are highly reactive nonmetals and react strongly with alkali metals.

• 7 valence electrons

Groups of the Periodic Table

• The elements of Group 18 of the periodic table are called the noble gases.

• Helium, Neon, Argon, Krypton, Xenon, & Radon.

• Gases at room temperature.

• These nonmetals are sometimes called the inert gases because they rarely take part in a reaction

• 8 valence electrons, except He that has 2

Groups of the Periodic Table

Lanthanides are metals that quickly dissolve in acid, ignite in air, and reacts with halogens, sulfur, 

hydrogen, carbon, and nitrogen upon heating

Groups of the Periodic Table

Actinides are metals that are mostly man-made in particle accelerators, many are radioactive and react with air.