Achemist needs 90 milliliters of a 72% solution but has only 68% and 77% solutions available. find how many milliliters of the 68% solution should be mixed with the 77% solution to get the desired strength.

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?