The element lithium has two stable isotopes, li-6 and li-7. how do the atomic structures of these two isotopes compare? a) both have 3 protons and 3 electrons, but li-7 has 4 neutrons. b) both have 3 protons and 4 neutrons, but li-7 has 4 electrons. c) li-6 has 3 protons and 3 electrons; li-7 has 3 protons and 4 electrons. d) li-6 has 3 protons, 3 neutrons, 6 electrons, while li-7 has 3 protons, 3 neutrons, and 7 electrons.

Two loudspeakers, 5.5 m apart and facing each other, play identical sounds of the same frequency. you stand halfway between them, where there is a maximum of sound intensity. moving from this point toward one of the speakers, you encounter a minimum of sound intensity when you have moved 0.33 m . assume the speed of sound is 340 m/s.part a) what is the frequency of the sound? part b) if the frequency is then increased while you remain 0.21 m from the center, what is the first frequency for which that location will be a maximum of sound intensity? express your answer to two significant figures and include the appropriate units.