Type of reproduction taking place with one parent

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

Given the following equation: 2a1 + 3mgcl2 --> 2alcl3 + 3mg how many moles of aluminum chloride are produced from 2.5 moles of magnesium chloride?

The atom fluorine generally will become stable through the formation of an ionic chemical compound by accepting electron(s) from another atom. this process will fill its outer energy level of electrons.