knowverseNoble gases already have a full outer shell, meaning they have nothing to gain by trading or sharing electrons. Every other atom reacts because it is trying to reach that same full shell.
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An atom's chemical behavior is almost entirely determined by its number of valence electrons in the outermost shell.
An atom's chemical behavior—how it reacts with others—is almost entirely determined by its number of valence electrons.
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If the valence shell is already full, the atom remains stable and ignores other atoms.
If the valence shell is already full, the atom will usually ignore all other atoms and stay by itself.
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Having eight electrons in the outer shell creates perfect balance, known as the Octet Rule.
This preference for the number eight is so consistent in nature that we call it the Octet Rule.
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Chemical reactions occur as atoms trade or share electrons to reach a stable octet.
A chemical reaction is essentially just atoms trading or sharing electrons to satisfy the Octet Rule.
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Helium is stable with only two electrons because its only shell is very small and full.
There is one small exception: Helium is perfectly stable with only two electrons because its only shell is very small.
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Sodium has one valence electron, making it unstable and reactive.
Sodium has only one electron in its outer shell. It is very unhappy and unstable with this extra 'loose' electron.
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Chlorine has seven electrons in its outer shell, leaving it one short of the stable octet.
Chlorine has seven electrons. It is just one short of the perfect eight.
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Atoms with eight electrons rest in a low-energy state, like a ball at the bottom of a bowl.
Atoms with 8 electrons are in a 'low energy' state, like a ball at the bottom of a bowl.
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Scientists can force noble gases like xenon to bond using extreme pressure and reactive elements like fluorine.
Scientists have used extreme pressure and highly reactive elements like Fluorine to force gases like Xenon to form bonds.
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The outermost boundary of an atom where electrons live is called the valence shell.
We call this outermost boundary of the atom the valence shell.
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An atom can have many layers of electrons, but only the one at the very edge is given this specific name. Because electrons are on the outside, they are the first parts of the atom to feel the presence of a neighboring atom.
Scientists often focus only on the count of these valence electrons because they are the particles that get traded or shared during a reaction. This outermost boundary dictates how an atom behaves when it encounters others in its environment.
An atom's chemical behavior. how it reacts with others. is almost entirely determined by its number of valence electrons. If the valence shell is already full, the atom will usually ignore all other atoms and stay by itself.
An atom's chemical behavior—how it reacts with others—is almost entirely determined by its number of valence electrons.
From the Knowverse course text.
For almost every atom, having exactly eight electrons in that outer shell creates a state of perfect balance. Most other elements do not start with eight electrons in their outer shell and are constantly searching for ways to fill those gaps.
This preference for the number eight is so consistent in nature that we call it the Octet Rule. Atoms with eight electrons rest in a low energy state, acting like a ball at the bottom of a bowl.
A chemical reaction is essentially just atoms trading or sharing electrons to satisfy the Octet Rule. Everything in our material world is a result of atoms trying to look like a noble gas.
This preference for the number eight is so consistent in nature that we call it the Octet Rule.
From the Knowverse course text.
There is one small exception to the rule of eight that appears frequently in nature. Helium is perfectly stable with only two electrons because its very small shell cannot hold any more.
Even though helium does not possess eight valence electrons, its outermost shell is still completely full. This full capacity provides the deeper physical reason for its remarkable stability over time.
While noble gases naturally avoid reacting, scientists can force them into bonds under extreme conditions. Researchers have used high pressure and reactive fluorine to make gases like xenon form compounds.
There is one small exception: Helium is perfectly stable with only two electrons because its only shell is very small.
From the Knowverse course text.
Sources: Foundations of Inorganic Matter. Each question or step includes an excerpt from the course.
