why lower orbital should be fillad up first? and how central metal atom can be separated from ligand in the coordination sphere ?

Total number of structural isomers of [Co(NH3)6][Cr(CN)6]

Why is boiling point of Cesium higher than that of Rubidium

which isomer mentioned in (a) is water soluble and why?

A gaseous mixture contains CO2 and CO the mass of the mixture is 200g and they are presenting equal fraction of moles . Find the total no. of O-atoms present in the mixture.

a gaseous mixture contains O2 , N2 and He in equal fraction of moles . Find the mass of He if 28g of N is present and 32g of O is present.