An atom has 25 protons 30 neutrons and 25 electrons what is the charge of the atom nucleus

Lets say that an object of a certain volume has a certin mass. what happens to its mass when you double its volume?

Idon’t quite understand this problem

Considering only the earth's rotation, determine how much later the asteroid would have had to arrive to put the explosion above helsinki at longitude 25˚ e? this would have obliterated the city.