Potential Energy of Ions in a Molecular Structure

[hy]

okay here's the equation:
In a certain molecular structure, the total energy E between two ions is given by

E= (-5.6/r) + 10e^(-r/3)
where r is the distance seperating the nuclei.


now i already sketched the graph but i don't know how to find the domain of E, or find values of r that make sense in the problem situation, or find the realative maximum or minimum values or the total potential energy on the interval (0, ∞) . the y in that interval is supposed to be infinite in case you can't tell what it is.

i tried to just look on the table but y never equals zero on there so I am lost. then i tried to just stick in zero for y on the equation. i got stuck .

 

[kreil]

you gave the equation, but what's the question that goes with it?

 

[HallsofIvy]

Do you know what "domain" means. And, as kreil asked, what was the question?