The natural isotopes of Iron are Fe-55 and Fe-56. If the average atomic mass is 55.85, what are the percent abundances of each isotope?

15%

85%

Explanation:

Let the natural abundance of Fe-55  = y

      the natural abundance of Fe - 56  = 1-y

Average atomic mass = 55.85

Unknown:

Percent abundances of each isotope = ?

Solution;

The average atomic mass of a substance is given as;

  Average atomic mass  =  (mass x abundance)Fe - 55 + (mass x abundance)Fe - 56

Now insert the parameters and solve;

55.85  = (55 x y) + [56 x(1-y)]

 55.85  = 55y + 56 - 56y

 55.85  = -y + 56

  55.85 - 56  = -y

  -0.15 = -y

     y  = 0.15

1-y  = 1 - 0.15  = 0.85

Percentage abundance;

   Fe - 55  = 0.15 x 100  = 15%

   Fe - 56  = 0.85 x 100  = 85%

b..

is the correct one

explanation:

covalent bonds form as valence electrons are shared between two atoms. lewis structures and structural formulas are common ways of showing the covalent bonding in organic molecules. formal charge describes the changes in the number of valence electrons as an atom becomes bonded into a molecule.

i think its 100

i hope this !