1) Pick the one with the largest radius.
Explain your selection using chemical principles
a. Ca2+ or Cl
b. As or Br
To determine which option has the largest radius, we need to understand the concept of atomic and ionic radii. In general, the size of an atom or ion is determined by how many electron shells it has and the effective nuclear charge it experiences.
Let's start with option a, Ca2+ or Cl. Calcium ion (Ca2+) is formed by losing two electrons from a neutral calcium atom. When electrons are removed, the effective nuclear charge experienced by the remaining electrons increases, causing the electron cloud to be pulled closer to the nucleus. This reduction in electron shells leads to a smaller ionic radius compared to the neutral calcium atom. On the other hand, chloride ion (Cl-) gains one electron to achieve a full valence electron configuration. This additional electron shell increases its ionic radius compared to the neutral chlorine atom.
Now, let's move on to option b, As or Br. Arsenic (As) and bromine (Br) are both elements in their neutral state. Arsenic is larger than bromine because it has more electron shells. Bromine is smaller because it has fewer electron shells than arsenic.
In summary, considering the principles of atomic and ionic radii, the option with the largest radius would be:
a. Ca2+ or Cl - The chloride ion (Cl-) has a larger ionic radius than the calcium ion (Ca2+).
b. As or Br - Arsenic (As) has a larger atomic radius compared to bromine (Br).
Remember, when comparing atomic or ionic radii, we should consider the number of electron shells and the effective nuclear charge acting on the outermost electrons.