Why are the levels of the mercury in the two arms of the U-tube the same when there is no gas in the flask?

Endeleev saw trends in the physical and chemical properties of elements when he organized them by

For the following dehydrohalogenation (e2) reaction, draw the zaitsev product(s) resulting from elimination involving c3–c4 (i.e., the carbon atoms depicted with stereobonds). show the product stereochemistry clearly. if there is more than one organic product, both products may be drawn in the same box. ignore elimination involving c3 or c4 and any carbon atom other than c4 or c3.

Why is carbon ideal for making different compounds?