首页>英语角 > 听力 > 美音 > 课 程 > 物理 > 硕士>How To Find Protons
How To Find Protons
Question
Atom is neutral.This is because it has
提交
Hi, I'm Donald Sinclaire. I'm a science teacher with Greater London Tutors, and today we're going to be looking at a few topics in chemistry. This is how to find protons in the atom. The atom consists of two main parts: a dense heavy nucleus, which sits in the center, and the electrons, which orbit around it. Here we have an atom of lithium. Lithium is the third element. It has an atomic number of three. That means it contains three protons. Protons here are drawn in green. They live in the nucleus, or the center of the atom, are positively charged, and are heavy compared to other particles. Also in the nucleus are neutrons, here in red. As the name suggests, neutrons have no charge. They're neutral. But they have a similar mass to protons and also exist in the nucleus. The nucleus is responsible for virtually all of the mass of an atom. It's also very small and very dense. If this diagram was drawn to scale, the nucleus would be so small as to be invisible. We draw it large here so you can see the individual particles. Virtually all the mass of an atom is concentrated in the nucleus. Orbiting the nucleus are electrons. Electrons are negatively charged, which is why they orbit the nucleus, because negative charges are attracted to positive charges. Electrons are also very light. They're approximately two-thousandths the mass of a proton or a neutron, and so add very little to the mass of the atom overall. Electrons orbit in layers, which fill up. Lithium has three protons, which means since an atom is neutral, it also has three electrons. Now, the first layer surrounding the nucleus can only take two electrons. So when you have three electrons, the third one has to go in the second layer. The electrons that are orbiting in the outermost layer are called valence electrons. These are the ones that determine the chemical properties of the atom. They're the ones that are responsible for forming bonds with other atoms to make molecules. Donald Sinclaire explains the structure of an atom. He shows how the atom consists of both a nucleus, with protons and neutrons, and an electron shell, with orbiting electrons.
视频文本已隐藏,本文本来自网络或网友仅供参考
显示视频文本

Discuss

0 comments
characters remainingSubmit
反馈