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Atomic Theory and the Nuclear Model

In chemistry, the atomic theory is a theory of the nature of matter, which states that matter is composed of discrete units called atoms. The word "atom" comes from the Ancient Greek adjective atomos, meaning "indivisible". The word "atom" itself comes from the Greek , "indivisible". The word was coined by the ancient Greeks as a result of their philosophical theories on the nature of the universe. The word "atom" was first used by the early Ionian philosophers, who used the word to describe the smallest unit of matter that cannot be divided into anything smaller. This fundamental concept was further developed in the 6th century BCE by the Pre-Socratic Greek philosopher Leucippus, who claimed that atoms were the fundamental constituent of all matter. Leucippus and his student Democritus (c. 460–370 BCE) argued that the fundamental constituents of the world were indivisible atoms which were constantly moving and interacting in empty space until they assembled into the objects we see around us.


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Video Transcript

Dalton's atomic theory states that all matter is made of atoms, which are indivisible. Atoms are made up of different numbers of neutrons, protons and electrons, and each element is made up of atoms that have a unique number of protons. So, for example, if we compare something like helium versus hydrogen, if we look at the periodic table, we can see that helium has two protons, while Arjun has one proton. And usually when we're indicating the number of protons, you'll usually find the number, um, located at the upper left corner next to the chemical simple. And so we can see that because helium and hydrogen have two different protons, these are two distinct elements. Um, in a different case, we can have an element that can have Adams with a different number of neutrons but can still be the same element because it has the same number of protons, which are called isotopes. So, for example, we can compare something like carbon 13 and carbon 14. And whenever you see a chemical symbol with a number in the upper right corner, this usually indicates the atomic weight off the atom. So if we compare carbon 13 with current 14. We still know that carbon has six protons or otherwise it won't be carbon. But if we look at the number of neutrons, Carbon 14 has eight neutrons. Because to calculate the number of neutrons, you take the atomic weight and subtract number of protons from it. And for cover 13 instead of eight neutrons, it has seven neutrons using the same formula and so we can see Yeah, thes two atoms can still be the same type of element, but they are different because they have neutrons and therefore are as the tips of each other. So since Adams are indivisible, it is also important to note that compounds exist as a combination of atoms and not a fraction of an addict. So, for example, if we look at carbon dioxide, which can be written as co two, um, the nature, we won't find something like see one half. Oh, so have a carbon bonded to oxygen because again, Adams are indivisible, and you will simply not find this, and it does not exist. Likewise, you can't have have a molecule. So whenever you're writing out in reaction and writing the number of bulls or trying to balance an equation. You can't put something like one half co two. So the smallest number of moles that you can have, uh, written before your molecule would be one. So that's something that keep in mind in the future when we're balancing equations.