According to Mendeleev’s periodic law, the elements were arranged in the periodic table in the order of:

In Mendeleev’s periodic table, gap was not left for one of the following elements. This element is :

The Newland’s law of octaves for the classification of elements was found to be applicable only up to the element :

The three elements having chemical symbols of Si, B and Geare :

In Mendeleev’s periodic table, gaps were left for the elements to be discovered later on. An element which found a vacant place in the periodic table later on is :