The Periodic Table

• Explain the roles of Mendeleev and Moseley in the development of the periodic table.

  
  

  •Describe the modern periodic table.

  
  

  
  

• 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.

• 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.

• 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 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 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.

• 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.

• 
  

• Explain the relationship between electrons in energy levels and the length of each period of the periodic table.

• Locate and name the four blocks of the periodic table.

• Describe the locations in the periodic table and the general properties of the alkali metals, the alkaline-earth metals, the halogens, and the noble gases.

• Elements are arranged vertically in the periodic table in groups (1-18) that share similar chemical properties because they have the same amount of valence electrons.

• Chemical properties are determined by the number of electrons in an atom.

• Elements are also organized horizontally in rows, or periods (1-7).

• The length of each period is determined by the number of electrons that can occupy the sublevels being filled in that period.

Groups 1,2 13-18 are also called, 1A-8A the group number in this format tells you the amount of valence electrons

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

• 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

• 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

• 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

• 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

• 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

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

hydrogen, carbon, and nitrogen upon heating

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

• The atomic radius is one-half of the distance between the nuclei of two atoms of the same element when the atoms are joined.

• ionization energy: the energy required to remove an electron from an atom in its gaseous state

• electronegativity: the ability of an atom to attract electrons when the atom is in a compound

• Atomic size, ionization energy, ionic size, and electronegativity are trends that vary across periods and groups of the periodic table.

• These trends can be explained by variations in atomic structure.

• The increase in nuclear charge within groups and across periods explains many trends.

• Within groups, an increase in electron shielding has a significant effect on these trends.