An average sample of coal contains 3.0% sulfur by mass. calculate the moles of sulfur present in 2.40 ´ 103 kg of coal.

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?

An atomic nucleus is composed ofa)protons.b)protons and neutrons.c)protons and electrons.d)protons, neutrons, and electrons.

Which statement best summarizes the importance of ernest rutherford’s gold foil experiment? it proved that all of john dalton’s postulates were true. it verified j. j. thomson’s work on the atomic structure. it showed that an electron circles a nucleus in a fixed-energy orbit. it showed that a nucleus occupies a small part of the whole atom.