When is alpha particle emission most likely to occur?
a. when the nucleus has more than 83 protons.
b. when the ratio of neutrons to protons in the nucleus is too high to be stable. c. when the nucleus has a mass of more than 83 amu.
d. when the ratio of neutrons to protons in the nucleus is not exactly balanced.

"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."