When radon-220 nucleus emits a gamma ray, what nucleus remains?

Gamma ray is an energy emission. In Gamma decay there is no any particle decay from the parent nucleus. It is just an unstable nucleus becomes as stable by releasing energy as photon. That energy releases as a gamma ray. Hence, there is no change in atomic number or mass number of the daughter atom.

Hence, radon (Rn) remains as same after undergoing a gamma decay but in less energy.

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm

i don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.