Are the noble gases?
a. elements with two valence electrons
b. elements with two or eight valence electrons
c. elements with seven valence electrons
d. elements with one valence electron

B. Elements with two or eight valence electrons.

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.

14 days is the half-life of phosphorus-32