What is the most abundant gas in earth's present day atmosphere?

methane
oxygen
carbon dioxide
nitrogen

Which statement is best described as a atom

The twister and runaway train are two coasters at the same amusement park. both coasters start at the same height. the coaster for the twister is twice the mass of the coaster for the runaway train. which roller coaster has greater gravitational potential energy at the start of the ride?

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