A shiny brown coloured element 'X' on heating in air becomes blackin colour. Name the element and the black coloured compoundformed

1- on heating solid yellow arsenic, it becomes a liquid , and by further heating from 100ºc   to 200ºc , it becomes solid black arsenic, by raising the temperature to 270ºc its colour becomes……greywhiteredviolet

The compound (X) on heating gives a colourless gas. The residue dissolved in water to obtain (Y). Excess CO2 is bubbled through aqueous solution of (Y), (Z), is formed. (Z) on gentle heating gives white (X). The compound (X) is :ACaCO3 BNa2CO3 CCaSO4.2H2O DK2CO3

A certain inorganic compound (A) on heating loses its water of crystallization. On further heating, a blackish brown powder (B) and two oxides of sulphur (C and D) are obtained.

Compound X is a colorless liquid at room temperature. A sample of pure X was slowly heated from -5℃, which is below its melting point, to 90℃, which is above its boiling point. Its temperature is measured every minute and the results are represented on the graph.

Name the element which:(a) is 78% of clean, dry air ........................................................................................................ [1](b) has atoms with an electronic structure of 2,8,1 ................................................................... [1](c) is extracted from hematite ................................................................................................... [1](d) forms an oxide with a giant covalent structure .................................................................... [1](e) is the gas with the slowest rate of diffusion at room temperature