Elements are chemical substances made up of the same types of atoms (atoms with the same proton number), whereas molecules are chemical compounds made up of atoms from two or more different elements. So now I know that molecules are made up of two or more atoms of different elements. So now, What about the elements? What is the number of atoms in an element? (When I say elements, I'm referring to the elements in the periodic table.) Aren't they what's known as an element? Please answer this question and help me clear my confusion and doubts, also mention the knowledge of atoms and elements from very basic.
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1$\begingroup$ You can have one atom of an element, such as a single gold atom. Or you can have many atoms of an element, such as in a piece of pure gold. In the ordinary oxygen gas you are breathing, two oxygen atoms are bonded to form an oxygen molecule. In ozone, three oxygen atoms are bonded together. Ordinary oxygen and ozone are elemental allotropes. $\endgroup$– Ed VAug 27, 2021 at 14:48
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1$\begingroup$ I think the problem here is that you are using a narrow (and therefore flawed) definition of molecule. Molecules consist of two or more bonded atoms. The definition is surprisingly subtle. Look up for instance IUPAC definitions of molecule. goldbook.iupac.org/terms/view/M04002 $\endgroup$– Buck Thorn ♦Aug 27, 2021 at 14:54
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1$\begingroup$ I was surprised not to find "what is a molecule?" answered on the site. However, that is not the question here. $\endgroup$– Buck Thorn ♦Aug 27, 2021 at 14:57
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$\begingroup$ @EdV, is O2 molecule or element? To be a molecule there have to be atoms of different elements, isn't it? $\endgroup$– Ashbin GiriAug 27, 2021 at 15:04
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4$\begingroup$ $\ce{O2}$ is a molecule. The atoms do not have to be different. $\endgroup$– Buck Thorn ♦Aug 27, 2021 at 15:19
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1 Answer
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Your definition of "molecule" is wrong and the question about the number of atoms in an element doesn't apply
Molecules can be made from a single element, they do not have to be made from multiple elements. But many pure elements can be made into more than one type of molecule and many don't usually form any discrete molecule under normal conditions. Molecules are better describes as discrete units containing a specific number of atoms and bonds whether made from the same element or not.
Carbon, for example, can appear as buckyballs (eg buckminsterfullerene 60, a football-shaped molecule with 60 carbon atoms joined as a mix of hexagons and pentagons in a regular polyhedral ball). But it more commonly appears as diamond or graphite where the bonds between carbon atoms form a near-infinite network which nobody describes as a "molecule". Oxygen mostly appears as a diatomic gas (two atoms bonded together) but sometimes appears as ozone (three oxygen atoms). Sulfur mostly appears as solids containing 8 sulfur atoms in a ring. Metals mostly form solids with no discrete molecules.
Different forms of the same element are called allotropes. So it doesn't make sense to ask "how many atoms in an element" as each allotrope is still a form of the element (which might contain discrete molecules or not and might contain molecules with different numbers of atoms).
Many substances (whether made from a single element or not) do not contain discrete molecules. And some elements appear in different forms some containing molecules and others not containing discrete molecules at all (see carbon). A substance containing only a single element is a form of the element. But many elements have multiple forms so you can't always go from element to molecule in reasoning about what form it takes.
answered Aug 27, 2021 at 16:48