<span>The number of protons in every atom of an element determines the atomic number of an atom. Short after Rutherford made the gold foil experiment, the British scientist Henry Mosely discovered that the atoms of every element have a unique positive charge in their nuclei. This positive charge is the number of protons and is called atomic number. So, the atomic number identifies every different element.</span>
I believe the answer is "After adding two substances together a new order is detected" because nearly all of the other answers suggest a chemical change has taken place. The reason I say "almost" is because answer two and four results in bubbles forming so the answer cannot be both. The only one to not clearly show a chemical change has occurred is the last answer.
