Two answers required. A narrow peak at an FT-IR vibration mode between these two elements indicates that metal soaps have crystallized on an oil painting. Two symmetric normal modes in a bond between these two elements combine and split in the most-studied Fermi resonance. A bond between these two elements bends at 15 microns at the low-energy endpoint of the infrared window. Nearby Lewis basic ligands or metals donate to the antibonding orbital between these two elements, reducing their bond frequency, in the textbook example of pi backbonding. (10[1])Bonds between these two elements (10[1])that stretch at 1700 inverse-centimeters (10[2])are (10[1])usually (10[2])the (10[1])strongest peaks in an infrared (10[2])spectrum. (10[1])A double bond between these two elements re-absorbs a large fraction of the infrared (10[1]-5[1])radiation reflected by the Earth in the greenhouse (10[2])effect. (10[4])For 10 points, name these two elements that are double-bonded in a (-5[1])ketone. ■END■ (10[1]0[1])