Help it’s past due please help

Why are the trends and exceptions to the trends in ionization energy observed?

Plz choose one of the compounds from the table and explain how you know the numbers of atoms in your formula. is it possible for two different compounds to be made from the exact same two elements? why or why not? with a limited number of elements (less than 120 are known), does this mean we also have a small number of compounds or do we have a large number of compounds in this world?

How many liters of water vapor can be produced if 108 grams of methane gas (ch4) are combusted at 312 k and 0.98 atm? show all work. pls ! will mark as brainliest