What determines what elements end up on the periodic table?

In numbering carbon atoms in the parent chain of a hydrocarbon, why would you number from right to left, rather than left to right

Melting and boiling are endothermic processes. this means that these processes absorb energy from their surroundings in order to occur. use this information and the data you collected in the phase change gizmo to describe what happens to the temperature of water when you boil it, then explain why this result occurs.

How many grams of magnesium metal will react completely with 8.3 liters of 5.5m hcl? show all work