Which of the following is the most basic oxide?

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

Of the following pairs,the one containing an example of metalloid elements in the periodic table is:

The electronic configurations of four elements are:
$I.$ $[Kr]\, 5s^1$
$II.$ $[Rn]\, 5f^{14}\, 6d^1\, 7s^2$
$III.$ $[Ar]\, 3d^{10}\, 4s^2\, 4p^5$
$IV.$ $[Ar]\, 3d^6\, 4s^2$
Consider the following statements:
$(i)$ $I$ shows variable oxidation state
$(ii)$ $II$ is a $d$-block element
$(iii)$ The compound formed between $I$ and $III$ is covalent
$(iv)$ $IV$ shows single oxidation state
Which statement is True $(T)$ or False $(F)$?

The periodic trend of chemical reactivity for alkali metals and halogens is described in the following statements. Which statement provides the correct concept?

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