Why does a new period start on the periodic table, instead of the row continuing? A. A new period starts when a new energy shell starts. B. A new period starts when a new neutron cycle starts. C. None of these D. It is based on how many protons it has.

Which statement is true about a catalyst? a: a catalyst decreases the rate of the reaction. b. a catalyst is consumed during a chemical reaction. c. a catalyst lowers the activation energy of a reaction. d. a catalyst increases the reactant concentration during a reaction.