Atomic Structure and Atomic Weight

In chemistry, an atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are very small; typical sizes are around 100 picometers. The word "atom" comes from the Greek (atomos), meaning "indivisible". In the past, the word "atom" was used for the smallest possible division of a substance, which was assumed to be indivisible. As modern chemistry developed, it became apparent that this assumption, while useful in many ways, was incorrect; it was found that atoms can be divided into smaller particles, such as electrons and protons, and that the nucleus of the atom consists of still smaller particles, such as neutrons and protons. The term "atom" is now used for two different concepts: a particle which is the smallest constituent unit of ordinary matter, and a set of particles which (as a whole) has a unique mass and composition, and which is almost always an electrically neutral system.

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Video Transcript

so items contain a core nucleus and electrons that move around the nucleus. So here I have an example of a helium atom, and a helium atom contains two protons as a labeled here and two neutrons, which I labeled here in its nucleus, as well as two electrons that move around the nucleus. So it's important in it that hydrogen is the only element that does not have any neutrons and only one proton and electron. But for any other element, they have both neutrons and protons in the new list. In addition to understanding the atomic structure, that's also important to understand what contributes to its weight. So the atomic weight is measured in a muse, and the majority of the atomic weight is from neutrons and protons. Eso If you wanted to find the number of neutrons, you would take the atomic weight, and from this value, subtract the atomic number, which all just right as number of protons s O. For example, if you wanted to figure out the number of protons and neutrons in carbon 12, we know that there are six protons in carbon. It would take the atomic weight 12 and subtract six we got six on DSO. There are six neutrons it six protons in carbon 12, um, as another example, if we have carbon 14 again, we still have six protons because carbon has six protons, but the atomic weight is 14 instead of 12. And so if we do out the math, we get eight. So Harmon, 14, has eight neutrons and 6%. And for our last example, if we have something like sulfur 32 theater comic number of sulfur is 16. And so if we do the same math, where the atomic weight is 32 we subtract the number of protons we get 16. So sold for 32 has 16 neutral and lastly, support to note that even though electrons are also a huge part of items that actually doesn't contribute to the atomic weight because the weight is so negligible. Eso the exact weight of an electron is 9.109 times 10 to the negative, 31 kg. And so if we think about it, the electron does not have any significant mass. That would actually change the atomic weight. And so we don't include this in our atomic weight calculation.