1. Now that we have learned about the Modern Atomic theory and understand what an atom is and what makes it up, and how it can be manipulated into different forms of itself. Let’s take a look at how the Periodic Table is organized and how this form of organization was developed.
The Periodic Table

2. Elements are arranged on the periodic table according to their properties.
First we should look at the periodic table and know that it is comprised of different elements, these elements are arranged on the periodic table according to their properties. So who came up with how to organize elements on the periodic table?

3. Discovering a Pattern
Dmitri Mendeleev, a Russian chemist, discovered a pattern to the elements in 1869.
Mendeleev arranged the elements by properties, and then by increasing atomic mass.
He noticed that when he arranged the elements according to mass, those with similar properties formed a repeating pattern.
Mendeleev found that the element’s properties followed a pattern that repeated itself every 7 elements.
He called his element arrangement a periodic table. Periodic means it happens at regular intervals.
In 1869 a Russian chemist knowing as Dmitri Mendeleev discovered a pattern to the elements. He arranged the elements by properties and then by increasing atomic mass. He noticed that when he arranged the elements according to their mass, those with similar properties formed a repeating pattern. Mendeleev found that the element’s properties followed a pattern that repeated itself every seven elements. He called his element arrangement the periodic table. Periodic by definition mean it happens at regular intervals in this case it was seven.

4. Changing the Arrangement
The periodic law states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements.
Mendeleev helped to really develop the periodic law which states that the repeating of chemical and physical properties of elements change periodically with the atomic number of the elements. Wait a minute, didn’t Mendeleev organize his table by atomic mass? Yes! However during Mendeleev’s time the proton had not been discovered so today the table is organized by atomic number rather than mass, surprisingly there are not that many difference in the order of the elements. Mendeleev even left spaces on the table to account for elements that have not been discovered yet, but he believed they would be discovered and he could explain their properties and he was right!