The specific heat capacities of F2(g), Cl2(g), Br2 (g), and I2 (g) are 0.824, 0.478, 0.225, and 0.145 JK^-1 g^-1, respectively. Compute the molar heat capacities of these elements and identify any periodic trend. If there is a trend, use it to predict the molar heat capacity of astatine, At2(g).