How are the elements are organized in the periodic table?
It's all about how many electrons an element has. Hydrogen has 1 electron, therefore it is the first in the table. It is also important that the elements are sorted into different categories, from left to right, alkali metals, nonmetals, metals, poor metals, gases and noble gases. In terms of how reactive they are the closer it is to the bottom left corner, the more reactive they are, whereas the top right corner is the least reactive. Lanthanoids and Actinoids are reactive metals but they are on the bottom of the table because it would be too long otherwise.