Ammonia (NH 3) is a weak base that reacts with a strong acid to form the ammonium ion, NH 4 +. If 5.00 mL of a solution of an ammonia cleaner is titrated directly with 42.6 mL of 0.5000 M HCl, what is the concentration of the NH 3 in solution? (Assume that the ammonia is the only solute that reacts with the acid.) a. 0.0587 M
b. 0.107 M
c. 4.26 M
d. 1.07 M
e. 5.87 M

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.

catya your not at all which answer i've seen you do this on another question!