7.An atom of sodium has 11 protons and 13 neutrons. Is it the most abundant isotope of Na? Yes

No

Yes, endothermic means it turns cold. and some chemical changes include change of tempature.

Conservation efforts have been effective in "increasing the number of endangered species, reducing all the negative impacts of human activity, and preserving wildlife habitats".hope my answer has you : ) 

If your on odysseyware i believe the answer would be c.