periodic properties - chem.boun.edu.tr · certain sets of properties recur periodically....
TRANSCRIPT
When elements are arranged in order of increasing atomic number,
certain sets of properties recur periodically.
•Metallic, nonmetallic and metalloid properties
• Atomic radius
• Ionization energy (energy necessary to remove the outermost electron)
• Electron affinity (energy change on addition of an electron to a neutral atom)
• Electronegativity
PERIODIC PROPERTIES
Metals
Good conductors of heat and electricity.
Malleable and ductile.
Moderate to high melting points.
Nonmetals
Nonconductors of heat and electricity.
Brittle solids.
Some are gases at room temperature.
Metalloids
Metallic and non-metallic properties
Classifying the Elements: The Periodic Law and the Periodic Table
•1869 Dimitri Mendeleev Lothar Meyer
Periodic Law
When elements are arranged in order of increasing atomic mass, certain sets of
properties recur periodically.
Meyer based his periodic law on atomic volume—the atomic mass of an element divided by the
density of its solid form
1869 Mendeleev
Mendeleev left blank spaces in his table for undiscovered elements, and
he corrected some atomic mass values
Groups (families)
Periods
Alkali Metal
Alkali Earth Metal
Noble Gas
Halogen
Members of element families have similar chemical properties because they have the same number of electrons in their outer energy levels.Hydrogen is usually considered separately.
8
2
8
18
Choose the Larger Atom in Each Pair
• C or O• Li or K• C or Al• Se or I
ELECTRONEGATIVITY
a measure of the tendency of an atom to attract a bonding pair of electrons
• The Pauling scale is the most commonly used. Fluorine (the most
electronegative element) is assigned a value of 4.0, and values range down to
Cesium and Francium which are the least electronegative at 0.7.
ELECTRON AFFINITY
the energy change when an electron is added to an atom
IONIZATON ENERGY
the energy necessary to remove the outermost electron of an atom
Tendency of metals to loose electon(s)
Tendency of non-metals to gain electron(s)
Cation is always smaller than atom from which it is formed.
Anion is always larger than atom from which it is formed.
Ionization Energies of Elements
Periodic Properties
• Melting and boiling points within a group
• Ability to conduct heat and electricity across a period
• Reducing and oxidizing abilities within a group
• Acid-base nature of element oxides
Other properties that relate to theperiodicity of elements