Which of the following atoms has the weakest attraction for electrons in a bond with a calcium (Ca) atom? a. Br atom
b. I atom
c. Cl atom
d. F atom

B- Iodine

Explanation:

Using the periodic trends, electronegativity (electron affinity) goes down as you go down a period. This is due to the atom gaining new shells when going down each period, resulting in a weakened attraction force between the nucleus and the electrons in the cloud. In other words. as more shells are added, the weaker the atom's affinity for electrons are and the less electronegative it is. As a result, Iodine would have the weakest attraction for electrons in a bond with Calcium as it is the furthest down in the periodic table.  

the ratio of the conjugate base to the acid required to attain the desired ph.

level 4 to level 2 : ))