Choose whether the reaction is exothermic or endothermic. 2C(s) + 2H2(g) → C2H4(9) -Select--
2H2(g) + O2(g) → 2H20() -Select--
N2(g) + 3H2(g) + 2NH3(g) --Select--

the answer to your question is c.

if you read the house of usher you should know that the house was haunted

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.

a polar bond is formed when electrons are shared unevenly between atoms