What factor was most important to Mendelev in knowing when to end a row (period) and start a new one?

The name of the ion, s2-, is: sulfurous ion sulfide ion sulfur ion sulfate ion

In vapor-liquid equilibrium in a binary mixture, both components are generally present in both phases. how many degrees of freedom are there for such a system? the reaction between nitrogen and hydrogen to form ammonia occurs in the gas phase. how many degrees of freedom are there for this system? steam and coal react at high temperatures to form hydrogen, carbon monoxide, carbon dioxide, and methane. the following reactions have been suggested as being involved in the chemical transformation:

How much carbon is stored in the atmosphere as co2