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.
Atoms are really small! Some atoms have more protons, neutrons, and electrons, and some have fewer. Depending on how many protons and electrons an atom has, the atom behaves differently. The simplest atoms have just one proton and one electron-that's a hydrogen atom. A bunch of these atoms together make hydrogen gas. More complicated atoms have more protons, more neutrons, and more electrons.