Discussion Topic Imagine a world in which all the elements existed, but they couldn't form any chemical bonds
with each other. What kinds of substances could exist in such a world? What kinds of
substances could not exist? What do you think this world would be like?

The identities of substances are the same before and after which type of change

Answer asap : ( a. how does mucus prevent the entry of pathogens? b. describe two ways white blood cells protect us from pathogens.

The image compares the arrangement of electrons in two different neutral atoms. a figure labeled atom q has a shaded sphere at the center of three concentric circles. the innermost circle has two black spheres. the middle circle has six black spheres. to the left of this figure is another figure labeled atom p. atom p has a shaded sphere at the center of three concentric circles. the innermost circle has two black spheres. the middle circle has seven black spheres. which of the following best explains the position of the two atoms in the periodic table?