1st Year Chemistry Study Material

                Periodic Table of Elements

The periodic table of elements is a chart that outlines all the basic elements of chemistry that make up our world according to their atomic numbers, the number of electrons each element has, and their predominant chemical properties.(1st Year Chemistry Study Material)

Each element is lined up from low to high atomic number, which simply refers to the number of protons it has. Most periodic table of elements charts are laid out in this fashion: A tabular grid of 18 by 7 that houses all of the major elements over another two rows of elements below it.

The table can also be broken down into 4 distinct parts or blocks: the s-block on the left, the p-block on the right, the d-block towards the middle and the f-block at the bottom.

The table rows are referred to as "periods" and the columns (s, p and d blacks) are called "groups." Some groups also have specific names such as the noble gases, or the halogens.

The name "periodic" table suggests that the table itself is open to being updated on a periodic basis, so it's not only used to uncover how each of the elements relate to one another but also to discover the characteristics of new elements or yet to be found or synthesized elements.

Therefore, the periodic table proves to be an important guide and resource when it comes to showcasing all the basic elements and studying chemical tendencies, and is commonly used not only in the science of chemistry but other fields of science as well.

Although other forms of the periodic table have been known to exist, Dmitri Mendeleev is typically recognized as the pioneer for publishing the first periodic table of elements in 1869. He designed the table to show similarities in the properties of the elements that were known back in the day. He also forecasted the properties of undiscovered elements back then and marked their place on the table, and in fact most of his claims and estimations proved true when the elements were discovered as time passed. Since the 1800's the periodic table has grown and improved with new elements being found and new theories explaining the way chemicals behave.

Elements from atomic number 1 to 118, hydrogen to ununoctium, have either been discovered or created. From all of these, all the elements you see up to californium occur naturally. Others have been created in labs. Chemists continue their pursuit to synthesize new elements way beyond ununoctium, but the presence of these synthesized chemicals having their place on the periodic table is still a question of continued disagreement and debate. Synthetic versions of elements that naturally occur in the earth have also been produced in chemical laboratories.

The above image of an eighteen column period table of elements structure is now the most commonly and broadly used format because it’s been so popular and widely accepted.

Also called the “long form” periodic table layout, it differs from Mendeleev’s short form design by removing the groups three to twelve and inserting them instead into the other major groups. The long form layout actually includes the actinides and the lanthanides in its structure instead of placing them below and away from the main table body. This wider layout table also adds two more periods, periods 8 and 9, and also incorporates the superactinides.

One thing to keep in mind is that the periodic table only documents chemical elements. It does not account for subatomic particles, or elements combined together such as mixtures and compounds. Each element's atomic number depends on how many protons it has in its nucleus. Isotopes are two or more variants of the same chemical element. They contain the same number of protons but carry a different number of neutrons in their nucleus. As the number of protons stays equal, the atomic number does not change. For example, carbon has three isotopes that occur naturally. Most have 6 protons but the number of neutrons can vary between 6 and 8. However, isotopes are always shown together under the element they belong to in the periodic table. Elements with no stable isotopes carry the atomic mass of the most stable isotope of that element, where the mass is displayed in parentheses.

(1st Year Chemistry Study Material)

Let’s take a closer look at the arrangement of elements in the table. As mentioned before, all the elements are arranged according to their rising atomic number, or their increasing number of protons. A new period or row begins when an electron shell gets its first electron. Groups or columns are arranged according to the number of electrons the atom carries. Also, elements that display comparable chemical characteristics usually also fall within the same column, and in the f and d blocks elements that lie in the same row to some extent also display similar characteristics. Therefore if you know the properties of a particular element it is fairly simple to figure out the properties of other elements that surround it in the table.

Here are some more facts about the periodic table:

According to the most updated version in 2012, the periodic table is said to have 118 elements. Of these 114 are official and have been named and documented by the International Union of Pure and Applied Chemistry (IUPAC).

Ninety-eight elements are naturally occurring out of which eighty-four are known as primordial elements. The remaining fourteen occur in decay chains of these primordial elements.

Even though elements like livermorium, flerovium and those listed from einsteinium to copernicium do not naturally occur in the earth and have been synthesized, they are still recognized by the IUPAC.

Other elements like 113, 115, 117 and 118 are known to be supposedly formulated in labs but the information has not yet been validated. Therefore these elements are only recognized by their element name, depending on their atomic number. As of the year 2012, there have been no reports of any element being synthesized keeping the count as of today at 118