Heads-up: Scientific people, please correct me if I'm wrong, since I'm just semi-informed layman. Hoping I don't offend anyone or cringe anyone up into a singularity, I lay my thoughts bare for the world to see:
All previous answers rely on the fact that chemistry and physics just goes away.. and I cannot fully partake in this.. I will allow just minor alterations in the physics of the universe, everything else is just going too far for me and if you want that, then please ignore what I'm about to write next...
Everything that lives, dies
As you've stated that no living thing would remain alive, this implies that ALL atomic bonds have been broken, no molecules survive.. asin.. literally ALL molecular patterns cease to be. This feat is nothing to sneeze at (if at all possible), but I will allow it in order to entertain us: Voiding all atomic bonds would break all molecules into it's constituent atoms, in this, there are a couple of scenarios I can come up with:
No more atomic bonds, permanently
You destroy the concept of atomic bonds forever and basically turn everything into transparent haze of atomic dust.. all forms of structures would disappear, and this is a good thing, since there would be no complex molecules left to support ANYTHING, thus collapsing in on itself, electron shells overlapping, probably either:
- some kind of high temperature bose-einstein condensate with unknown properties
- a low-pressure neutron core, much like a neutron star, only bigger in radius and lower in density
- a singularity, since there are no molecular bonds anymore, you basically throw away all repulsive properties of electrons as well and atomic nuclei are allowed to touch, either collapsing together like the earlier mentions neutron core, and at high enough pressures to overcome the strong force, a fusion reaction, causing the entire planet to go bang like a mini supernova.
No more atomic bonds, (extremely) briefly
If you only disrupt the atomic bonds but a Planck Second, all matter would violently re-connect to it's molecular counterpart for the most part (except for some boundary layers where substances would mix, if possible and not disturbed by the violent nature of atomic bonding) and release a tremendous amount of heat, basically breaking down every molecule and atom into a plasma, blowing up the planet in a violent explosion caused by the thermal pressure of the instant plasma.
Near Infinite Gamma Ray Annihilation PewPew Beam
If you just kill life by irradiating it so hard that 100% of all life (remember, this shit is TOUGH) is dead by method of focusing the combined energy a couple of thousands Gamma Ray Bursts onto the planet (only 1 will yield you 99,99% results, so you'll have to do this a couple of thousand times over to get anything approaching 100% on a molecular level) you either:
- Put so much energy into the planet that the thing basically turns into a plasma ball, exploding violently by the extreme thermal pressure of the entire planetary sized plasma ball.
- If somehow, no heat is transferred from this Gamma Ray Annihilation Beam, and no heat is caused by the friction of atoms and and no particles will recombine because you can keep this beam on long enough (or let it simmer away), you will probably end up with atomic dust either being blown away by the beam or by turbulence in the system itself, turning into a ring of dust around the sun.
I'm no physicist or mathematician, but I know that in order to kill every group of molecules that has the potential for abiogenesis, you will have to dump an AWEFUL lot of energy into your target, in this case an entire planet. The whole "ball of plasma violently exploding under the radiation pressure"-theme is popping up a lot of times when I run simulations in my head.
Stuff just doesn't die for no apparent reason.. Life is really tough.
But again, since is is a ridiculous fantasy situation and the fact that I couldn't mathmatically formulate ANYTHING I stated above (even if my life depended on it), everything is just 100% pure speculation based on known physics.