Ca, V, Cu, Kr
Remember a period is a the horizontal rows in the Periodic Table.
Answer:
A. non fiction or a ajami to download
If the ending substance has changed its properties. For example if iron rusts it is a chemical change because it is no longer the same as before it is now just rust. A physical change only changes the appearance but burning something or changing it's chemical properties is a chemical change.
The answer is B "the reaction is exothermic", and C "the reactants lost internal energy."