Inside the Atom: Protons, Neutrons and Electrons

<h3>What is an atom made of?</h3><p>An <strong>atom</strong> is the smallest particle of an element that still behaves like that element. Although atoms are far too small to see, scientists have shown that each atom is built from three smaller particles called <strong>sub-atomic particles</strong>.</p><ul><li><strong>Proton</strong> &mdash; found inside the nucleus, carries a <strong>positive</strong> charge, relative mass of 1.</li><li><strong>Neutron</strong> &mdash; found inside the nucleus, carries <strong>no</strong> charge (neutral), relative mass of 1.</li><li><strong>Electron</strong> &mdash; moves in shells outside the nucleus, carries a <strong>negative</strong> charge, relative mass of about <code>1/1840</code>.</li></ul><p>The <strong>nucleus</strong> is the small, dense centre of the atom. Because the protons and neutrons are packed there, almost all of the atom's mass is in the nucleus. The electrons take up most of the space but add almost no mass.</p><p>In a neutral atom the number of protons equals the number of electrons, so the positive and negative charges cancel out exactly.</p><div class="callout"><strong>Kenyan context:</strong> Aluminium used to make cooking <em>sufurias</em> and roofing sheets (mabati) is element number 13. That means every aluminium atom has 13 protons and, when neutral, 13 electrons. Knowing this helps engineers in Kenya predict how the metal will conduct heat and electricity.</div>