Define Newlands' law of Octaves.

Arrange the following elements in the order of their increasing nonmetallic character:
$Li, O, C, Be, F$

Three elements $X$,$Y$,and $Z$ having atomic numbers $11$,$7$,and $6$ respectively react with oxygen to form their oxides.
$(a)$ Arrange these oxides in increasing order of their basic nature.
$(b)$ Give reason for your answer.

Two elements $P$ and $Q$ belong to the same period of the modern periodic table and are in Group $1$ and Group $2$ respectively. Compare their following characteristics in tabular form:
$(a)$ The number of electrons in their atoms
$(b)$ The sizes of their atoms
$(c)$ Their metallic characters
$(d)$ Their tendencies to lose electrons
$(e)$ The formula of their oxides
$(f)$ The formula of their chlorides

Give reasons for the following:
$(a)$ Lithium atom is smaller than Sodium atom.
$(b)$ Chlorine (Atomic Number $17$) is more electronegative than Sulphur (Atomic Number $16$).

Which of the following is the outermost shell for elements of period $2$?