Select the correct statement about isotopes. a. all the isotopes of an element are radioactive. b. isotopes of the same element have the same atomic number but differ in their atomic masses. c. all the isotopes of an element have the same number of neutrons. d. isotopes occur only in the heavier elements.

Option (B) is the correct answer.

Explanation:

Isotopes are the substances or species that contain same number of protons but different number of neutrons.

As it is known that atomic number means the total number of protons present in an atom. Hence, this also means that in isotopes atomic number of the species is same.

For example, isotopes of hydrogen are , , and .

Isotopes of only heavier elements are radioactive in nature as they have large difference in the number of protons and neutrons.

Thus, we can conclude that the statement isotopes of the same element have the same atomic number but differ in their atomic masses, is correct.

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.