What indicates that a chemical reaction has taken place explain why the indicator would be a sign of chemical reaction is not a sign of physical change

For ai it's atomic number is 13 and it's mass number is 27 how many neutrons does it have

Which of the following observations indicates that there is a small, dense, positively charged part in the center of an atom? some uncharged particles are scattered by a gold foil. all uncharged particles are attracted towards a gold foil. all positively charged particles pass straight through a gold foil. some positively charged particles bounce back from a gold foil.

20 pts ‼️ an unmanned spacecraft travels to mars. mars has a lower strength of gravity than earth. where in the image is the spacecraft’s weight the greatest?