Chemistry Lab/Periodicity

This page is related to the 2012 focus on periodicity for Chem Lab.

Basic Information
Periodicity is the backbone of the Periodic Table. It means "a repeating pattern that is at regular levels." The Periodic Table is ordered by certain chemical and physical properties. These periodic trends may increase or decrease by element, depending on the way one moves along a row or column.

The Periodic Table
For a picture of the Periodic Table, see Periodic Table.

The periodic table was first ordered by Dimitri Mendeleyev in 1869. It grouped the elements known at the time into families, based on similar chemical properties, and left spaces blank for future elements to be discovered.

The Periodic Table is arranged by rows (or periods) and columns (or groups). Periods are arranged by atomic number, and groups are ordered by similar chemical properties.

Groups
Groups are ordered from 1 to 18 (new IUPAC numbering), and these correspond to the number of valence, or outer, electrons that the element has.

Some groups have names, which are dependent on chemical properties.

Special Blocks
There are also certain blocks of elements that have special names.


 * The Lanthanoids and the Actinoids are the elements at the very bottom of the short form of Mendeleyev's Periodic Table.
 * The Lanthanoids are elements 57-71
 * The Actinoids are elements 89-103
 * The Lanthanoids and part of the Actinoids (up to Uranium) are known as Rare Earth Metals
 * Elements past Uranium are known as Trans-Uranic


 * Boron, Silicon, Germanium, Arsenic, Antimony, and Tellurium are known as semi-conductors.
 * With Polonium, these seven elements are known as metalloids.


 * Elements in Groups 13-16 that are not categorized are just simply known as "other metals/non-metals."

Some examples of Periodic Trends

 * Atomic Radius: distance from nucleus to outermost electron; increases as one moves down a period, and from right to left.
 * Ionization Energy: amount of energy required to move one electron from an atom; increases as one moves up a period, and from left to right
 * Redox properties: the possibility the element will be involved in a redox equation; increases as one moves outward from the center of the table

Links
Nice explanation of a few periodic properties