Periodic Table

The periodic table of elements is a way of organizing the chemical elements in periods and groups according to their properties. For example: a highly reactive element can be found on the table next to another highly reactive element. These are called halogens, but we'll get to those later. The periodic table goes from left to right in periods according to the number of protons in the nucleus of an atom of that element. As you move from left to right in a period, the number of protons from element to element increases.
This is all well and good, but what about conductivity or reactivity? Well, as you reach the end of a period, the number of valence electrons (electrons in the outer electron shell of that element's atom" increases.What does this mean? Well, when an atom's outer electron shell is full, that means that is not very reactive. When the outer shell of an atom is filled all the way, it is called a noble gas. These are the least reactive of the elements. Right to the left of those are the halogens, highly reactive elements. They are so reactive due to the fact that their outer electron shells are not filled to the maximum, but by just barely. This means that another element's atom with an electron to fill that gap in the halogen's electron cloud can react with it so easily.