If you start with
29 g, how much will
be left after 3
half-lives?

3.625g

Explanation:

The definition of a half-life is the time required for any specified property to decrease by half. Given that the question asks for the amount of grams left after 3 half-lives, not the amount of time it takes for 3 half-lives to pass, it can be assumed that it is basically asking what the final value will be when 29g is reduced by half 3 times.

This is shown by the following sequence of equations:

29/2 = 14.5 (after 1 half-life)

14.5/2 = 7.25 (after 2 half-lives)

7.25/2 = 3.625 (after 3 half-lives)

Therefore, the answer is 3.625g.

idk i’m struggling too

"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."