For a reaction to occur, energy must be to break chemical bonds.

a. converted

b. released

c. absorbed

The correct answer is absorbed.

Explanation:

Bond formation is a type of exothermic process. In these reactions when two atoms come close to each other, energy is released in this process.

On the other hand, in the breaking of bond, energy is required because the atoms are to be separated from each other. This is a type of endothermic process. So, the energy must be absorbed.

Hence, the correct answer is absorbed.

"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."