The Separate Parts of the Periodic Table

by Paul Dohrman

Overview

The Separate Parts of the Periodic Table

During the 1860s, chemists found that arranging the elements by mass gave rise to repeating, or periodic, properties. Among various representations proposed, Dmitri Mendeleyev's, published in 1869, has stood the test of time because of its economy, correctness and ability to predict new elements.
Noble Gases

Other elements strive to have complete outer electron shells as the noble gases do, dropping or adding a few electrons to do so. Therefore, the periodic table conceptually centers on the noble gases despite being in the far-right column.

Halogens and Alkali Metals

An example of this filling of outer shells to achieve greater stability are the halogens (second-last column) and alkali metals (first column), which combine easily by sharing the alkali metal's extra electron.
Halogens

Because halogens are so close to having full outer shells, they are also reactive with metals in general.
Metalloids

The metalloids consist of B, Si, Ge, As, Sb, Te and Po. They get their name from sharing metallic and nonmetallic qualities with each other.
Transition Metals

The transition metals are distinguished from the group "other metals" (in green) because their electron configuration easily gives up what are called "d" electrons, which makes them good electrical conductors.