The most commonly used diagnostic tool for tuberculosis is a simple skin test, though blood tests are becoming more commonplace. A small amount of a substance called PPD tuberculin is injected just below the skin of your inside forearm. You should feel only a slight needle prick.
The structure has a double bond and an adjacent atom with a lone pair, so it could have resonance. The possible resonance structures are below. The first structure has the most common bonding pattern for all of its atoms, so it is a reasonable Lewis structure.
We will consider resonance a possibility for molecules and polyatomic ions that have the following as part of their Lewis structure. 1  Z can have more than one lone pair. 2  X and Y can have lone pairs. 3  The X-Y bond can be a triple bond. 4  Z cannot be F with one bond and three lone pairs or O with two bonds and two lone pairs.