How does the concentration of hydroxide ions compare to the concentration of hydronium ions in pure water?

What is the percentage composition of carbon in the compound ch4

The number to the right of an element's symbol (ex. c-12) identifies the of an isotope.

Select all of the statements which are true. electrons are located in shells or orbits around the atom. electrons orbit slowly around the atom. electrons travel in one flat path around the nucleus of an atom. the valence of an atom is determined by the number of electrons in the atom's outermost shell.