Valence (chemistry) facts for kids
Valence (say: VAY-lence) is a super important idea in chemistry! It tells us how many chemical "hands" an atom has to hold onto other atoms. Think of it like this: atoms connect to each other using special links called chemical bonds. Valence is simply the number of these links an element's atom can make.
For a long time, scientists believed that each element had a fixed number of bonds it could form. For example, they thought carbon always made four bonds. Oxygen was believed to always make two bonds, and hydrogen always one.
But then, they found something interesting! Some elements, like phosphorus, could make a different number of bonds depending on the situation. Sometimes phosphorus would make three bonds, but other times it would make five! This showed that valence wasn't always a fixed number for every element.
What is Valence?
Valence helps us understand how atoms combine to form molecules. It's like a rule that tells us how many partners an atom can have in a chemical dance.
For example, a hydrogen atom usually has a valence of one. This means it can form one bond. An oxygen atom usually has a valence of two, so it can form two bonds. A carbon atom often has a valence of four, meaning it can form four bonds.
When atoms bond, they try to fill their "outer shell" of electrons. Valence helps us predict how atoms will share or exchange these electrons to become stable.
Valence Can Change
Because some elements can form different numbers of bonds, scientists needed a better way to describe this. The IUPAC (a big group of chemists) came up with the idea of "oxidation numbers".
Oxidation numbers are a bit like a more detailed way to describe how many bonds an atom is making in a specific chemical compound. It helps chemists understand how electrons are shared or moved around in a molecule. This idea helps explain why elements like phosphorus can act differently in various chemical reactions.
Related pages
Images for kids
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A methane molecule. Carbon (black) has a valence of 4, bonding with 4 hydrogen atoms (white).
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An acetylene molecule. The two carbon atoms (black) share three bonds with each other.
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The structure of sulfuric acid. Sulfur (yellow) can have different valences depending on the compound.
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William Higgins' ideas about how atoms combine (1789).
See also
In Spanish: Valencia (química) para niños
