1. different form of an element.   placebo   serendipity   whorl   isotope   Hint Half-n-half Clue   2. optical illusion due to atmospheric conditions.   symmetry   velocity   transition   mirage   Half-n-half Clue   3. smallest particle of a substance with all its properties.   molecule   yield   touchstone   increment   Half-n-half Clue   4. residue from smelting operation.   slag   molecule   symbiosis   terminology   Half-n-half Clue   5. topmost point or summit.   mirage   serendipity   vertex   prototype   Half-n-half Clue   6. mental disorder.   transition   psychosis   touchstone   indices   Half-n-half Clue   7. tube with patterns from colored glass piece reflections.   kaleidoscope   medium   stratum   solstice   Half-n-half Clue