Calculate the molarity (M) of an aqueous solution that is 12.8% by mass NaCl, given that the density of the solution is 1.08 g/mL.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.