<span>401 K
The equation that expresses the vapor pressure of a liquid is the Clapeyron equation:
Tb = (1/T0 - (R ln(P/P0))/Hvap)^(-1)
where
Tb = boiling point at pressure of interest
R = Ideal gas constant
P = vapor pressure of the liquid at the pressure of interest
P0 = known pressure at T0
Hvap = heat of vaporization
T0 = boiling temperature
So let's substitute the known values and calculate.
Tb = (1/T0 - (R ln(P/P0))/Hvap)^(-1)
Tb = (1/391K - (8.3144598x10^-3 kJ/(K*mol) ln(1.39atm/1atm))/42.3 kJ/mol)^(-1)
Tb = (1/391K - (8.3144598x10^-3 kJ/(K*mol) ln(1.39))/42.3 kJ/mol)^(-1)
Tb = (1/391K - (8.3144598x10^-3 kJ/(K*mol)*0.329303747)/42.3 kJ/mol)^(-1)
Tb = (1/391K - (2.73798276760652x10^-3 kJ/(K*mol))/42.3 kJ/mol)^(-1)
Tb = (1/391K - (6.47277250025181x10^-5 1/K))^(-1)
Tb = (2.49281703203073x10^-3 1/K))^(-1)
Tb = 401.152586471767 K
Rounding to 3 significant figures gives a boiling point of 401 K</span>
Atoms of metals do not hold their electrons to themselves. Instead they allow them to float around them delocalised. This is important because it is this characteristic that allows metals to be good conductors of electricity since electrons are free to move around to carry a charge.