Scientists often look at how much isotopes of have decayed to help estimate the age
of a fossil or once-living material.

Scientists often look at how much of isotopes of : Carbon-14  have decayed

To determine the age of fossils archeologist make use of the carbon-14 dating ( i.e. making use of naturally occurring radioisotope ¹⁴C ) which is used to determine the age of fossils or material that were once in living on earth.

Carbon has about three (3) isotopes ( Carbon-12, Carbon-13 and Carbon-14 ) .but Carbon-14 isotope is most useful in determining the age of fossils and once-living things

Hence we can conclude that scientists often look at how much of isotopes of Carbon-14 have decayed to help estimate the age of fossils.

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If im correct it’s radioisotope

Explanation:

hloride, what is the mass of calcium in

explanation:

"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."