By extrapolating Charles's law and locating the x-intercept on the Kelvin scale, one can find this temperature, which cannot be reached by any physical apparatus.
In VSEPR ("vesper") theory, there are this many lone pairs on the central atom in trigonal bipyramidal molecules. Each element in group 2 of the periodic table has this number of valence-shell p-orbital electrons. In natural units, this is the dipole moment of a homonuclear diatomic molecule. When an element undergoes beta decay, its mass number changes by this much. To the nearest integer, this is the pH of one-molar nitric acid. By extrapolating Charles's law and locating the x-intercept on the Kelvin scale, one can find this temperature, which cannot be reached by any physical apparatus. For 10 points, give this number, also the number of neutrons in the lightest isotope of hydrogen.
In VSEPR ("vesper") theory, there are this many lone pairs on the central atom in trigonal bipyramidal molecules.
zero [or obvious equivalents like none, etc.; accept absolute zero]