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What is a Molecule?


What exactly is a molecule? Is it different from an atom? What about a compound? Although these words are easy to mix up, they all mean different things.


A molecule is formed when two or more atoms form a chemical bond with one another. Molecules are neutral, meaning their positive and negative charges are balanced. A molecule that is positively or negatively charged is called an ion, just like a positively or negatively charged atom.


Molecules can be very simple or extremely complex. For example, two nitrogen atoms bonded together forms the simple molecule dinitrogen. Glucose, a type of sugar, is more complex; it is composed of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms. DNA, which forms our genetic code, is what’s called a macromolecule. It’s so large that it contains billions of atoms. 



(PublicDomainPictures, 2013)


Molecules are named after the number of atoms in their makeup. For example, carbon dioxide is composed of one carbon atom and two oxygen atoms, making it a triatomic molecule. Molecules must have a determinate number of atoms in them, even huge macromolecules like DNA. Structures that use an unknown, indeterminate number of atoms, like some crystals, are not considered molecules.


Compounds are molecules that are made from different types of atoms. For example, a molecule like dinitrogen would not be a compound, because it only contains nitrogen atoms. However glucose, which contains hydrogen atoms, carbon atoms, and oxygen atoms, would count as compound. Compounds and molecules are somewhat like squares and rectangles. All compounds are molecules, but not all molecules are compounds.


Although molecules are made of atoms, single atoms are also not considered molecules. Molecules must contain multiple atoms.


Image Citation:


PublicDomainPictures (artist). (2013). DNA Biology Science [digital art]. Retrieved from

dna molecule.jpg
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