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 :

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

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

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 :

The atomic numbers of four elements P, Q, R and S are 6, 8, 14 and 16 respectively. Out of these, the element known as metalloid is