Neutron bomb

A neutron bomb was a nuclear weapon that, according to the First Doctor, "destroy[ed] all human tissue, but [left] the buildings and machinery intact." It was also shown to destroy the tissue of other organic matter, such as Time Lords and Thals.

On Skaro, neutron bombs were used in the neutronic war between the Dals and the Thals. (TV: The Daleks) Created thanks to the large deposits of cobalt the Daleks had discovered, these eventually caused the humanoid Daleks to mutate into the "machine Daleks". (COMIC: Genesis of Evil)

Human historians, who gave little credence to the story of the Humanoid Daleks, believed that the first generation of Daleks had, in the immediate aftermath of the Thousand Year War, detonated a neutron bomb to wipe out the remaining Thals only to underestimate the weapon's radioactive yield, trapping them in the newly built Dalek City for over five centuries. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) When the Daleks discovered that the bomb's effects had made them dependant on radiation, they sought to detonate another but abandoned this plan when its construction time was deemed too long. (TV: The Daleks)

The War Lords' Security Chief decided to use a neutron bomb to destroy the humans' resistance movement, but the Second Doctor saved them by transporting them in a SIDRAT to Central control. (TV: The War Games)

In the 1970s, the Third Doctor used a neutron bomb on the Moon to destroy the Daleks' base there. (COMIC: The Disintegrator) In 1980, a "neutron super-bomb" was being tested on Earth as part of mounting tension between the West and Iran. (COMIC: Dr. Who's Time Tales)

Steven Taylor found something he believed was "some kind of neutron bomb" inside the Monk's TARDIS. He speculated that it would be fired by the Monk's atomic cannon. (TV: "Checkmate")

Behind the scenes

 * In Inside a Skaro Saucer (one of the features from The Dalek World which, due to not being a story as such, is not considered valid by this Wiki), it was stated that each Dalek flying saucer contained a neutron bomb as a "suicide unit"; if the Dalek craft risked capture, it was to be activated, destroying the ship utterly and thereby erasing any chance that the enemy might be able to copy Dalek technology.
 * The Discontinuity Guide claims that, at least in the timeline before the Fourth Doctor interfered with the Daleks' creation, the Thousand Year War was ended following Davros' death at the hands of the Daleks when the Thals exploded a single neutron bomb, causing destruction so great that the Thals themselves were affected by the radiation, committing themselves to pacifism as a result. A group of advanced Daleks survived the explosion by leaving the planet in a hastily constructed spacecraft whilst more primitive Daleks, early products of Davros' experimental program, remained on Skaro before they were destroyed in a failed attempt to wipe out the Thals 500 years later.