What's the valency of sulphur for Na2SO3

Which is the layer underground where all empty spaces are filled with a combination of air and water ?

The wave shown on the electromagnetic spectrum disturb the medium it passes through a)different frequency. b)the same frequency .

The human eye contains a molecule called 11-cis-retinal that changes shape when struck with light of sufficient energy. the change in shape triggers a series of events that results in an electrical signal being sent to the brain that results in vision. the minimum energy required to change the conformation of 11-cis-retinal within the eye is about 164 kj/mol.