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