The Atomic Nucleus

<p><strong>The Field Guide to Particle Physics <br></strong><a href="https://pasayten.org/the-field-guide-to-particle-physics">https://pasayten.org/the-field-guide-to-particle-physics</a><br>©2021 The Pasayten Institute <a href="https://creativecommons.org/licenses/by-sa/4.0/">cc by-sa-4.0</a><br>The definitive resource for all data in particle physics is the Particle Data Group: <a href="https://pdg.lbl.gov">https://pdg.lbl.gov</a>.</p><p>The Pasayten Institute is on a mission to build and share physics knowledge, without barriers! <a href="http://pasayten.org/heysean">Get in touch</a>.</p><p><strong>The Atomic Nucleus</strong></p><p>We are made of molecules, and molecules are made of atoms, and atoms are really, really small. Atoms are so small that its hard for our minds to comprehend it, but if you need a reference point take your height and divide it by a billion. Or maybe ten billion! Atoms are too small to rationalize.</p><p>When we think about atoms, we model them as a nucleus surrounded by an <a href="https://pasayten.org/the-field-guide-to-particle-physics/the-electron-cloud">electron cloud</a>. Today, we are talking about that nucleus.</p><p>The nucleus is the hard center of the atom. It’s much, much smaller than the atom itself: about 100,000 times smaller. It's so small that if the atom were a baseball stadium, the nucleus is smaller than the baseball at the pitcher’s mound. Actually, the nucleus is more like a grain of clay atop of the pitcher’s mound.</p><p>Despite this small size, the nucleus makes up over 99% of the mass of the atom. So the nucleus is really, really small <em>and </em>really, really dense.</p><p>The nucleus is made up of smaller particles: <a href="https://pasayten.org/the-field-guide-to-particle-physics/proton">protons</a> and <a href="https://pasayten.org/the-field-guide-to-particle-physics/neutron">neutrons</a>. Different atoms have different numbers of both, and they are all bound together by a strong force - the aptly named strong nuclear force - a force much strong