Periodic+table

The periodic table is a table that contains all of the elements arranged in order of increasing atomic number. You can access a copy of the periodic table from page 6 of your databooklet.

The periodic table consists of vertical columns and horizontal rows. All of the elements in the same group have the same number of outershell electrons. This means that, all group 1 elements have 1 outershell (valence) electron, group 2 elements have 2 and so on. Because all the elements in the same group have the same number of valence electrons, all elements in the group have similar chemical properties (as the chemical properties of an element are dependent on the number of electrons in its outershell).
 *  columns are called groups and the rows are called periods.

All of the elements in the same period have the same number of electron shells. As you go across a period the atomic number of the elements increases by one. Therefore as you go across the period the each element will have one more electron than its previous element. //For example// as you go across period 3, Mg has one more electron than Na. Al has one more electron than Mg. All of the elements in the period 3 have 3 electron shells. Therefore, the period number indicates the number of shells that the element has. Just like the name suggests as you go across the ‘periodic’ table, there are certain trends in the properties of the elements in the periodic table.
 * The elements in the **first group** of the periodic table are known as **alkali metals**.
 * The elements in the **one to the last group** of the periodic table are known as **halogens**.
 * The elements in the **last group** of the periodic table are known as **noble gases**.

The properties of the elements and their trends as you go across the period or down the group is going to be studied in more detail in the next pages.

By the end of this lesson you should be able to:
 * State that the elements are arranged in order of increasing atomic number in the periodic table.
 * Distinguish between the terms period and group.
 * Know that the group number represents the number of outer shell electrons and that the period number shows the number of electron shells.


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The periodic table photo taken from (and edited): [] (accessed 12/02/2012).