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 which is just below the above element in the periodic table?

Arrange the acids $H_2SO_4$,$H_3PO_4$,and $HClO_3$ in the decreasing order of their acidic strength.

Similarity in chemical properties of the atoms of elements in a group of the Periodic table is most closely related to

Considering the elements $F,$ $Cl,$ $O,$ and $N,$ the correct order of their chemical reactivity in terms of oxidizing property is:
$(a)$ $F > Cl > O > N$
$(b)$ $F > O > Cl > N$
$(c)$ $Cl > F > O > N$
$(d)$ $O > F > N > Cl$

Given below are the oxides:
$Na_{2}O, As_{2}O_{3}, N_{2}O, NO$ and $Cl_{2}O_{7}$
Number of amphoteric oxides is ..... .

An element $X$ belongs to the fourth period and fifteenth group of the periodic table. Which of the following statements is true?