What is an element?

Do you find salt (NaCl) in the periodic table? But you do find ‘Na’ and ‘Cl’, isn’t it?

Do you find H₂O in the table? But there is H and O.

Seperation

You can separate salt from a mixture of salt and sand, isn't it?

The process of sorting substances from one another in a mixture is called separation. We apply the separation technique often in our daily lives.

If you have two or more substances present together and they can be separated esily, we say the substance is impure or it is a mixture of substances.

On the other hand, if the substance cannot be separated any further using any method, we can say that the substance is pure or it is made up only that substance.

But there is a problem in defining a pure substance in this way. The problem is that you may have tried all the methods that you know about today for separating a substance. Maybe the substance cannot be separated by any of these methods. So you think the substance is pure. But it is possible that a scientist could discover a new method of separating such a substance in future. It is possible that the substance you thought was pure today could then be separated into different substances, using this new method.

Consider this example. You draw water from a well and pass this water through a filter paper. The water passes through without leaving a deposit. What would you conclude at this stage about the purity of this water?

Next, you heat this water. All the water evaporates, leaving behind some deposit.
Would you still conclude that this water is pure?
This is what has been going on in the chemistry world. Chemists have been working in this manner with several substances and discovered new ones.

For example when you apply electrolysis, you find the water can be broken down or separated into hydrogen and oxygen. Since you cannot further separate hydrogen and oxygen you believe that they are the fundamental constituent substances. We started calling them into Elements. * (about electrolysis)

Let's learn about the discovery of phosphorus

The period was 17th century.
 

It was believed that human urine may contain the Philosopher's Stone, that has the ability to turn any metal into gold. It made an alchemist in Germany very curious. His name was Hennig Brand. He wanted to find a method to separate this Philosopher's Stone from urine.

This is what he did-

He let the urine stand for days  until it gave off a terrible smell. Then he boiled it down to a thick paste. He heated this paste to very high temperature and let the vapours cool under water. the vapours cooled to form a waxy substance that glowed in the dark!!!

This was Phosphours, the 13th element discovered.

In thsi way, chemists tried to separate substances using every known method available. When the substance could not be separated further, they concluded that they had found the basic substance or the building blocks of the matter around us. These fundamental substances were called Elements. 

The discovery of these elements led the scientists to another question about the differences among these elements. For example, how does hydrogen differ from oxygen? But before we find that out, let's learn about the naming of these elements.