Identify the most acidic oxide among the following oxides based on their reaction.

How do you determine the chemical reactivity of a compound? Provide an example.

In a periodic table, how does the basic character of oxides vary?

How many elements in the periodic table are gases? Provide their positions in the periodic table.

The increasing order of reactivity among group-$1$ elements is $Li < Na < K < Rb < Cs$ whereas that among group-$17$ elements is $F > Cl > Br > I$. Explain.

Use the periodic table to answer the following questions.
$(a)$ Identify an element with five electrons in the outer subshell.
$(b)$ Identify an element that would tend to lose two electrons.
$(c)$ Identify an element that would tend to gain two electrons.
$(d)$ Identify the group having metal,non-metal,liquid as well as gas at room temperature.