Question

what is the formula for dichlorine heptoxide?

Explanation:

Step1: Analyze prefixes

"Dichloro" means 2 chlorine atoms ($\text{Cl}$), "heptoxide" means 7 oxygen atoms ($\text{O}$).

Step2: Write formula

Combining the number of atoms, the formula is $\text{Cl}_2\text{O}_7$.

Answer:

$\text{Cl}_2\text{O}_7$ (the option $\text{Cl}_2\text{O}_7$)