The four natural isotopes of iron have atomic masses of 53.9, 55.9, 56.9, and 57.9. If these were the only isotopes of iron and they occurred in equal abundance, which would be closest to the atomic mass of iron? A. 54
B. 55
C. 56
D. 57

The ozone molecule o3 has a permanent dipole moment of 1.8×10−30 cm. although the molecule is very slightly bent-which is why it has a dipole moment-it can be modeled as a uniform rod of length 2.5×10−10 m with the dipole moment perpendicular to the axis of the rod. suppose an ozone molecule is in a 8000 n/c uniform electric field. in equilibrium, the dipole moment is aligned with the electric field. but if the molecule is rotated by a small angle and released, it will oscillate back and forth in simple harmonic motion.what is the frequency f of oscillation?