Which of the following is different in two isotopes of the same element? the number of atoms
the number of electrons
the number of neutrons
the number of protons

Different number of neutrons

Explanation:

Isotopes are different versions of an element, in which the only difference is that they have different numbers of neutrons in the nucleus, and therefore slightly different atomic masses.

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.