Which statement is correct? A. Atomic radius decreases down group 17.
B. First ionization energy decreases down group 1.
C. Atomic radius increases across period 3 from Na to Cl.
D. First ionization energy decreases across period 3 from Na to Cl.

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.

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