The Periodic TableChapter 3

Periodic Law

Law stating that many of the physical and chemical properties of the elements tend to recur in a systematic manner with increasing atomic number.

Mendeleev: Father of the Periodic Table

Mendeleev is best known for his work on the periodic table; arranging the 63 known elements into a Periodic Table based on atomic mass, which he published in Principles of Chemistry in 1869

He realized that the physical and chemical properties of elements were related to their atomic mass in a 'periodic' way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table.

Mendeleev provided for variance from strict atomic weight order, left space for new elements, and predicted three yet-to-be-discovered elements including eke-silicon and eke-boron.

Henry Mosely

Mendeleev’s table was nine tenths of the way there, but needed one important modification before it became the modern periodic table - the use of atomic number as the organizing principle for the periods.

Using atomic number instead of atomic mass as the organizing principle was first proposed by the British chemist Henry Moseley in 1913

Organization of the Periodic Table Horizontal rows in the table are referred to as

Periods. Hydrogen is period 1, Lithium is period 2, etc.

Vertical columns in the table are Groups or Families. Group 1 is called alkali metals, except H Group 2 is called alkaline earth metals Group 17 are called halogens Group 18 are called noble gases Groups 1,2,13-18 are called main group elements Groups 3-12 are called transition metals

Metals, Nonmetals, Metalloids

The periodic table is further divided into two broad categories of metals and nonmetals. Metals make up a majority of the table. Between the dividing line there is a class of elements that have properties of both metals and nonmetals. These elements are referred to as metalloids.

Non metals: halogens, noble gases, H, C, N, O, P, S, Se

Metalloids: B Si, Ge, As, Sb, Te, Po,*(At) Metals: The remainder of the elements Actinides: all of the elements following actinium Lanthanides: all of the elements following lanthanum