Typical diameters: nucleus: 10-14 – 10-13 m electron cloud: 10-10 m QUESTION: Which of the following subatomic particles are found in the nucleus of an atom? A. protons and neutrons B. protons and electrons C. neutrons and electrons D. protons, neutrons, and electrons Currently accepted model of the atom: protons and neutrons are in the nucleus. Electrons move around the nucleus. Regions between nuclei are mostly empty space. SCRIPT: Which of the following subatomic particles are found in the nucleus of an atom? A. protons and neutrons B. protons and electrons C. neutrons and electrons D. protons, neutrons, and electrons PAUSE CLICK. In the currently accepted model of the atom, protons and neutrons are in the nucleus, while electrons move in the mostly empty space outside the nucleus. The correct answer is A. Let’s imagine what atom looks like by imagining two atoms that are as close to each other as possible. Here’s the nucleus of one atom. CLICK And here’s the nucleus of the other atom. CLICK Each individual electron will be a dot much smaller that the ones shown here for the nucleus. However, because electrons move so fast and it is impossible to pinpoint the location of an electron, it is customary to represent them by drawing something that looks like a clouds around the nucleus. Each atom is comprised of a nucleus and the electron cloud that surrounds it. CLICK CLICK The diagram shown here is exaggerated. If we were to draw it to scale, it won’t fit your screen. The typical nucleus has a diameter of about 10-14 to 10-13 meters, depending on how many protons and neutrons it has while the typical electron cloud has a diameter of about 10-10 meters. In other words, the typical electron cloud diameter is at least one thousand times larger than that of the nucleus. This means if we can magnify one of the nuclei to the size you see on your computer screen --- about 1 millimeter diameter --- then the neighboring nucleus should be about one to ten meters away. Furthermore, the diameter of each individual electron is estimated to be less than 10-18 meters, …. That’s less than 100 thousand times smaller than that of a typical nucleus. So, the clouds we’re showing here are, in fact, mostly empty space. Typical diameters: nucleus: 10-14 – 10-13 m electron cloud: 10-10 m electron: <10-18 m

Video ID: 1-10-1 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08