Chapter 6 notes
The Periodic Table
Dobereiner – attempted to classify the elements in 1817.
Triad – three elements with similar propertiesThe middle element has an atomic mass about halfway between the other two.
Newlands in 1863 arranged the elements in order of increasing atomic masses
Appeared to be a repetition every eighth element
7 elements into 7 groups Law of Octaves
Mendeleev – properties of elements were a function of atomic masses
Left blank spots
Correctly predicted properties and masses of unknown elements
Mendeleev, the “Father of the periodic table”
Moseley– Found atomic number and problem solved!!!
Periodic Law – properties of the elements are a periodic function of their atomic numbers
Periodic table from 1930
This is how our table is organized today
Periodic Table
• Groups or families are columns that have elements with the same number of valence electrons
• Periods or series are rows on the chart. The properties vary.
• 8 main groups• Transition elements• Rare earth elements
Metals
Tend to Lose electrons
General rule–3 or fewer electrons in the outer levelLeft side of table
Alkali metals group 1
Alkali earth metals group 2
Nonmetals tend to Gain
electrons
5 or more electrons in the outer levelRight on the table
Halogens and Noble gases
Metalloids
Have properties of both metals and nonmetals
Located on ladder like line on table (not Al)
Examples of periodic law
• Metallic vs. nonmetallic character
• Size of atoms
Periodic Table
Each time a new energy level is started, a new row in the table begins
Lanthanoid series
Z = 57 to Z = 70
2 electrons in outer level4f sublevel
Actinoid Series
Z = 89 to Z = 102
5f sublevel
Ionization Energy
• To form a cation (a positively charged ion) an electron must be removed from the atom
• Ionization Energy—the energy needed to remove an electron from a gaseous atom
• A higher ionization energy means that an atom likes to hold onto its valence electrons
Group 1 elements (Li, Na, K, Rb) have low ionization energies, while the noble gases (He, Ne, Ar, Kr, Xe)
have high ionization energies
Ionization Energy• After removing one electron, it is possible
to remove another. This is called second ionization energy.
• Each successive removal of an electron has a higher ionization energy.
Ionization Energy
• Trends:– Within a period: ionization energies generally
increase across a row.– Within a group: ionization energies generally
decrease down the columns.
• Octet Rule: atoms tend to gain, lose, or share electrons to get a full set of 8 electrons
Electronegativity
• Liking for electrons when bonded