Which of the oxidation state$(s)$ is/are shown by the element sulphur?

Explain the periodicity of valence or oxidation states and explain the oxidation states of oxygen in $Na_2O$ and $OF_2$.

Describe the periodic trends in the valence of elements with respect to their oxides and hydrides.

In any period,the valency of an element with respect to oxygen:

Which of the following elements exhibits a constant valency?

Two elements $X$ and $Y$ have the following electronic configurations: $X = 1s^2, 2s^2 2p^6, 3s^2 3p^6, 4s^2$ and $Y = 1s^2, 2s^2 2p^6, 3s^2 3p^5$. The expected compound formed by the combination of $X$ and $Y$ is: