Which best describes h2(g) + cl2(> 2hci(g), h= -184.6 kj/mol?
a. the reaction has no activation energy.
b. the reaction is endothermic.
c. the reaction requires heat.
d. the reaction produces heat.

With the largest atoms and the smallest number of valence electrons and with the smallest atoms and the greatest number of valence electrons are the most reactive. a. nonmetals; metals b. nonmetals; transition elements c. transition elements; metals d. metals; nonmetals