Table:
text: Protactinium
Chemical compounds
Chemical compounds
Formula color symmetry space_group No_ Pearson_symbol a_pm b_pm c_pm Z density_g_cm3_
Pa silvery-gray tetragonal I4/mmm 139 tI2 392.5 392.5 323.8 2 15.37
PaO  rocksalt Fm3m 225 cF8 496.1   4 13.44
PaO2 black fcc Fm3m 225 cF12 550.5   4 10.47
Pa2O5 white  Fm3m 225 cF16 547.6 547.6 547.6 4 10.96
Pa2O5 white  orthorhombic   692 402 418  
PaH3 black cubic Pm3n 223 cP32 664.8 664.8 664.8 8 10.58
PaF4 brown-red monoclinic C2/c 15 mS60    2 
PaCl4 green-yellow tetragonal I41/amd 141 tI20 837.7 837.7 748.1 4 4.72
PaBr4 brown tetragonal I41/amd 141 tI20 882.4 882.4 795.7  
PaCl5 yellow monoclinic C2/c 15 mS24 797 1135 836 4 3.74

Question: What is the formula for a protactinium compound that has a density of only 3.74 g/cm^3?

Question: What is the formula for the compound that has the same Pearson symbol as Pacl4 under protactinium?

Question: What is the combined total density of Protactinium pao and pao2?