Each model shows bonding between a pair of atoms. Model A Two atoms are bonded side by side. The center of each is a mass of red and blue balls. Surrounding the centers are three concentric circles. The left atom has 2 pairs of electrons on the left side of the inner ring; 4 pairs of electrons evenly spaced on the center ring, and 4 pairs of electrons evenly spaced on the outer ring. The pair on the right side of the outer ring is shared with the atom to the right, which is a mirror image of the left atom. Model B The first of 2 atoms has a small ball of red and blue balls as a center, a ring around it with electrons at the north and south positions, and an outer ring with an electron at the northeast position. A wavy red arrow points from that electron to an open space in the outer ring of the second atom, which has a larger red and blue center, two electrons in the inner ring, and 7 electrons in the outer ring. Which statement best explains how the models differ?