Why periodic table is known as periodic table?

The word periodic means regular. It relates to the periodic table of elements in the following different ways:

The periodic table is known as the periodic table because it is based on the periodic law and because it is arranged so that the elements show periodicity of properties in it.

The horizontal rows in the periodic table are called the periods of the periodic table.

The periodic law says that "the physical and chemical properties of elements are the periodic functions of their atomic numbers." The modern periodic table is based on this law. That is why the periodic table is called periodic. In simple words, the periodic law means that when elements are arranged in ascending order of their atomic numbers, they show similarities in properties after regular intervals.

The phenomenon called periodicity of properties occurs in the modern periodic table. This is related to the above mentioned periodic law. In this phenomenon, the elements as arranged currently in the periodic table show similarities in their properties after regular intervals in the periodic table. These periodic properties also show a gradual variation in groups and rows of the periodic table. They are called the trends in the periodic table.

The periodic properties repeat themselves in the periodic table after regular intervals. These periodic properties are atomic size, ionization potential, electro-negativity, electron affinity, etc. These properties vary across rows and columns of the periodic table.

For example, the atomic size of elements decreases as we move from left to right across rows in the periodic table. This is because the number of shells remains same throughout each row of the periodic table whereas the atomic number increases. Due to this the attraction of the protons in the nucleus on the outer electrons of the atoms increases and therefore the outer shells come closer to the nucleus. Thus, the atomic size of elements atoms decreases as we move from left to right across a row of the periodic table.

Thus, the periodic table is called periodic because of the phenomenon of periodicity of properties in which certain properties of elements, called periodic properties, repeat themselves periodically throughout the periodic table.