Which of the following is NOT a property of phosphorus? Select the correct answer below: A. Phosphorus reacts directly with halogens, forming trihalides and pentahalides. B. Phosphorus is an inert nonmetal. C. Phosphorus forms two common oxides, P4O6 and P4O10. D. Phosphorus exhibits oxidation numbers that are unusual for group 15 elements.

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.