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--

Astable electron arrangement for an atom is one that does not easily change. how is this arrangement arrived at? a. valence electrons are transferred or shared to create a full outer shell of electrons. b. valence electrons are discarded into space to create a full outer shell of electrons. c. protons (positive charge) pair with valence electrons (negative charge) to create a strong bond. d. outer shells with valence electrons are transferred or shared.