The periodic table of elements is something that every chemist must be familiar with. However, if you’re unfamiliar with science in general, deciphering the table with all its letters, numbers and symbols may seem like a daunting task. Today, for those of you interested enough to be reading this blog, I will be writing a comprehensive guide on how to read the periodic table. Enjoy.
The periodic table is simply an arrangement of all the known chemical elements in a table, ordered based on their different properties and characteristics. Before we go into how the different elements are arranged, you should first understand the structure of an atom, which you can read about here in my previous post: An-atom-y.
You will be able to find periodic tables with lots of additional content, but there are only three fundamental pieces of information in each cell of the table. These are: the element symbol – the letters which represent the element, the atomic number (at the top – the number of protons in an atom of the element), and the relative atomic mass (at the bottom – the mean mass of an atom of an element compared to 1/12 the mass of an atom of carbon-12). Most elements have differing numbers of neutrons among different atoms; these variants are called isotopes. The relative atomic mass is determined by taking an average mass of all the isotopes of the element.
As we go from left to right and top to bottom of the table, like you are currently reading this page, the atomic number of the elements increase, which means that each successive element has one extra proton than the previous; this also means that they have one extra electron. As I mentioned earlier, however, each shell of an atom can only be occupied by a certain number of electrons, and it is the outermost shell of electrons that we are most interested in. This is what determines columns of the table, known as the periods.
Ignoring the weird indentation of the table in the middle section, there are eight groups (columns), each corresponding to the number of electrons in the outer shell of the atoms. All of the elements in a single group generally react in the same kind of way because they have the same number of electrons in their outer shell. Some of these groups are given specific names for ease of use. For example, the rightmost group is known as the Noble Gases, and all of the elements are extremely unreactive. Helium is an exception to this, but I will not dwell too deep. Going down the table, the periods (rows) represent the number of shells the atom has. In some periodic tables, you may see hydrogen floating around somewhere at the top, but you can consider it as being at the top left, above lithium.
The weird indented bit in the middle contains what are called the Transition Metals. The extra two rows at the very bottom are also part of the transition metals, but scientists couldn’t find anywhere to fit them in. They get a bit complicated so I’m not going to write about them either. As of now, there are 118 different elements in total. However, 24 elements (most of which are near the bottom of the table) are synthetic and do not exist in the natural world.
If you’re interested in finding out any more about anything I’ve missed out, please don’t hesitate to ask me or have a hunt online.