A beam of electrons is fired at a crystal of magnesium oxide, and photographic film is used to record the places where the electrons come through the crystal. Which of the following changes to the experiment is not likely to change the interference pattern that results on the film?

increasing the length of time the beam is fired at the crystal

Explanation:

Interference pattern does not depend on duration of the recording, though this might affect clarity of the image on the photographic film. Other things will change where the electrons end up. Speed of electrons affects its momentum, and thus its position. Proton has different mass, so different interference pattern. A different crystal will create a different interference pattern depending on the molecular formula.

a. patterns can explain observations.

"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."