The electronic configuration of an element is $1s^2 2s^2 2p^6 3s^2 3p^3$. What is the atomic number of the element that lies immediately below this element in the periodic table?

Red hot carbon will remove oxygen from the oxides $XO$ and $YO$ but not from $ZO$. $Y$ will remove oxygen from $XO$. Use this evidence to deduce the order of activity of the three metals $X, Y$ and $Z$ putting the most active first.

The characteristics of elements $X$,$Y$ and $Z$ with atomic numbers,respectively,$33$,$53$ and $83$ are :

The size of $Be^{2+}$ and $Al^{3+}$ is not so close,but they show a diagonal relationship due to:

The correct order of metallic character is:

Which one is the strongest acid?