An undiscovered element has three naturally occurring isotopes of x-55, x-57, and x-58. isotope x-55 has an abundance of 27.80 % and isotope x-57 has an abundance of 44.39 %. what is the average mass of this element in amu?

The average atomic mass of this elements is 56.7221 amu.

Explanation: The average atomic mass is the sum of the masses of its isotopes each multiplied by their natural abundances.

           .....(1)

We are given 3 isotopes of an element.

For Isotope ,

Mass = 55 amu

Fractional abundance = 0.2780

For isotope ,

Mass = 57 amu

Fractional abundance = 0.4439

Total Fractional abundance = 1

For isotope ,

Mass = 58 amu

Fractional abundance = Total abundance - abundances of the other isotopes

Fractional abundance = 1 - 0.7219

                                     = 0.2781

Now, putting all the values in equation 1, we get

Average atomic mass = 56.7221 amu.

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

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