Atoms

• If Atoms Are Mostly Empty Space, Why Doesn’t Light Pass Through Everything?
  Atoms are not hard little obstacles, but their electrons interact with light. A material’s structure and energy levels determine whether it transmits, absorbs.
• Why Does Halogen Reactivity Decrease Down the Group?
  Halogen reactivity usually decreases down the group because larger, more shielded atoms attract incoming electrons less strongly than smaller ones.
• Are Molecular Mass and Molecular Weight the Same?
  Molecular mass and molecular weight are often used interchangeably in chemistry, but molecular mass, relative molecular mass, and molar mass mean different things.