# Question #f918d

Jul 3, 2017

The molecular formula tells us two things: which elements are present in the compound and the ratio of elements.

#### Explanation:

The molecular formula $A l C {l}_{3}$ tells us that the compound aluminum chloride contains the elements aluminum (Al) and chlorine (Cl).

The formula also tells us that the ratio of aluminum atoms to chlorine atoms is 1:3. For every aluminum atom, there are 3 chlorine atoms.

The molecular formula ${N}_{2} {O}_{5}$ tells us that the compound dinitrogen pentoxide contains the elements nitrogen (N) and oxygen (O).

The formula also tells us that the ratio of nitrogen atoms to oxygen atoms is 2:5. For every 2 nitrogen atoms, there are 5 oxygen atoms.