Answer:
Sound waves are travelling vibrations of particles in media such as air, water or metal. So it stands to reason that they cannot travel through empty space, where there are no atoms or molecules to vibrate.
Explanation:
The number 90 has 1 sig fig.
Answer: 20 protons,20 electrons and 21 neutrons
Explanation: because the number of protons is the same as the atomic number, and if the atom is neutral it has the same number of protons and electrons. if the mass number is 41 it means that there are 21 neutrons because to find the mass number you have to add protons and neutrons, so 20 + 21 = 41 and to confirm it the neutrons have been subtracted from the mass number and the atomic number, so 41-20 = 21