Cliff Notes I. The Atom A. atom: the smallest unit of an element that keeps the properties of that element 1. "atom" comes from the Greek word "atomos" which means "not able to be divided" B. a single penny has 20,000,000,000,000,000,000,000 atoms in it II. Inside the Atom A. all atoms are made of the same 3 subatomic (smaller than an atom) particles: -protons, neutrons, electrons B. nucleus: the positively charged center of the atom C. Inside the nucleus are protons (+ charge) and neutrons (neutral charge) -protons weigh exactly one atomic mass unit (AMU) -neutrons weigh approximately 1 AMU as well D. Outside the nucleus are electrons (- charge) moving around in an electron cloud -electrons weigh approximately 0 AMU (basically nothing because they're so small) |