The periodic table of elements is an arrangement of all the known chemical elements in a tabular manner. These elements have been arranged in a number of columns (known as groups) and rows (known as periods). The arrangement is according to the properties of the elements, for example, elements with similar properties are listed close to each other, and all the noble gases are part of the last group, while all the alkali metals (such as sodium, potassium, etc.) are part of group I. Moreover, there is a trend of properties in a particular group or period. For example, the atomic radius increases as we move down a group, while it decreases as we move across a period. Due to this unique layout and orientation of periodic table, we can even have spaces for as yet undiscovered elements, based on their properties.
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