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

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

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

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 :

The three imaginary elements X, Y and Z represent a Dobernenner’s triad. If the atomic mass of element X is 14 and that of element Y is 46, then the atomic mass of element Z will be :