Atoms and ions of different elements always have different numbers

a. electrons

b. neutrons

c. protons

d. masses

Use examples from the article to explain one positive and one negative effect that chemistry has had on society

Which function is performed by earths atmosphere? a. ultraviolet rays are prevented from reaching the ozone layer. b. earths temperature is raised and moderated by trapping in heat c. charged particles from the sun are prevented from reaching earth. d. magnetic charges from space are prevented from reaching earths surface.

Which traits do human embryos have that link them to a common ancestor with fish and reptiles? a. scales and tail b. gill slits and scales c. tail and gill slits d. hair and tail