What are the most important inorganic molecular substances for living beings?

water, mineral salts, carbon dioxide and molecular oxygen.

water and minerals such as Iron, Phosphorus, sodium, Zinc, Calcium, Nitrogen...
Blood plasma contains92% water which helps in distribution of heat throughout the body.
Iron for haemoglobin thus important in oxygen distribution, phosphorus in bone formation, Sodium is essential in nervous coordination, acid-base balance and osmoreglation Zinc is important for insulin form and function and serve as enzyme co-factor (carbonic anhydrase), Calcium is important in bone and cartilage formation,part of blood clotting cascade and in muscle contraction, Nitrogen is important in protein synthesis.
There are other inorganic elements such as cobalt, manganese etc The most important inorganic substances for living beings are water, mineral salts, carbon dioxide and molecular oxygen.
There are several other inorganic substances without which cells would die.
some of them are listed above