What atomic or hybrid orbitals make up the sigma bond between si and h in silane, sih4?

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

it means there are 3 atoms of oxygen

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.