Radiation with a wavelength of 4.2nm

How many atoms are in 1.4 mil of phosphorus trifluoride (pf3)

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line

What shape would a molecule with two bound groups and two lone pairs have?