List of top Science Questions on Periodic Classification of Elements asked in UP Board X

Which is a non-metal in the following?
Arsenic element is:
Write the atomic number and valency of the following elements:
(i) Oxygen
(ii) Potassium
Write atomic number and valency of the following elements: (i) Nitrogen (ii) Magnesium
Na, Mg, and Al are the elements in which the numbers of valence electrons are one, two, and three respectively. (a) Which of these elements has the maximum atomic radius? (b) Which of these elements is the least reactive? Answer each with the reason.