In sociology and psychology, some definitions include only consciously malignant forms of discrimination. Some definitions of racism also include discriminatory behaviors and beliefs based on cultural, national, ethnic, caste, or religious stereotypes.
A cell is much, much larger than an atom. A typical animal cell might be 10,000 times as wide, long, and tall as a typical atom, or about 1 trillion times the volume of an atom. Another way to arrive at this answer is to consider the fact that cells are made up of atoms, so the atoms must therefore be smaller.
Cl- has the smallest radius due to the fact that atoms' radii get smaller as you go up and to the right in the periodic table. When atoms have the same electronic configuration(after gaining or loosing electrons) such as the ones you asked about, you will usually be able to compare their sizes by looking at their original position.