The radioactive isotope Uranium-235 has a difference of in comparison to Uranium-238. A) 3 less Neutrons
B) 3 Less Protons
C) 3 Less Electrons
D) No mass change, only a change in charge

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.

As changes in energy levels of electrons increase, the frequencies of atomic line spectra they emit