They all have a full outer shell of electrons, making them very stable (they tend not to react with other elements). These elements all line up in the eighteenth or last column of the periodic table. One example of a group is the noble or inert gases.
There are 18 columns or groups and different groups have different properties. Groups are the columns of the periodic table. In each period the left most element has 1 electron in its outer shell and the right most element has a full shell.
The first one is short and only has two elements, hydrogen and helium. There are seven (or eight) total periods. When they are lined up this way, elements in the columns have similar properties.Įach horizontal row in the table is a period. Some columns are skipped in order for elements with the same number of valence electrons to line up on the same columns. From left to right elements are lined up in rows based on their atomic number (the number of protons in their nucleus). It is called 'periodic' because elements are lined up in cycles or periods.
