Apositron is a particle similar to an electron, but with the opposite charge of an electron. if a positron and an electron collide, sometimes both the electron and positron disappear, and two photons are created. this is an example of

Annihilation of matter

Explanation:

Matter is annihilated when it collides with its antiparticle leading to a tremendous release of energy. This contradicts the law of conservation of matter which states that matter can neither be created nor destroyed.

"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."