The electron configuration of Zr (AN 40) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d2 5s2
1) An endothermic reaction is a reaction where heat is "absorbed" and the surrounding area is cooled. An example of an endothermic reaction is the classic baking soda and vinegar reaction. The mixture gets cold.
An exothermic reaction is one which gives off heat, such as burning, which is itself a chemical reaction.
2) (I don't actually know this one but i hope i helped with number one)
The baseball is thrown twice as fast as the softball in the same direction.
