An element ‘A’ on exposure to moist air turns reddish - brown and a new compound 'B' is formed. The substance 'A' and 'B' are

An element 'A' on exposure to moist air turns to form compound 'B' Which is reddish brown . Identify 'A' and 'B'.

When iron is exposed to moist air, a reddish brown substance is deposited on it. What is it ? Give its composition.

Two elements sometimes can form more than one compound .

Element 'A' and 'B' form a compound with cubic structure in which 'A' atoms are at the corners of the cube and 'B' atoms at the face centres. What is the formula of the compound ?

The electronic configuration of metal A is 2,8,18,1. The metal A when exposed to air and moisture forms B a green layered compound. A with conc. H_2SO_4 forms C and D along with water . D is a gaseous compound. Find A , B, C and D .