If you have remained attentive during your science classes in school, you must have heard your teacher speak about atoms and molecules. But the problem is that very few of you probably remember these.
Key Takeaways
- An atom is the smallest unit of an element that retains the chemical properties of that element.
- A molecule is a group of two or more chemically bonded atoms.
- Atoms are the building blocks of molecules and can exist independently, while molecules require at least two atoms to exist.
Atom vs Molecule
The difference between an atom and a molecule is that an atom is the smallest particle in any element and possesses the element’s properties. Breaking down an atom further and retaining the element’s properties is not at all possible. Conversely, molecules are the result of the combined efforts of two or more atoms.
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One of the primary differences between molecules and atoms is that the former latter cannot be divided further than the former. An example of atoms and molecules would be water.
It is a molecule with a combination of two atoms of hydrogen and one atom of oxygen.
Comparison Table
| Parameter of Comparison | Atom | Molecule |
|---|---|---|
| Definition | An atom is the smallest and the most fundamental unit of any ordinary matter. | Molecules comprise two or even more atoms that are bound together by a chemical bond. |
| Structure | An atom is the smallest of all particles possessing the same properties as an element. | Molecules are a combination of a minimum of two atoms. |
| Constituent Elements | It constitutes protons, neutrons, and electrons. | It constitutes a minimum of 2 atoms of the same element. |
| Stability | Atoms have electrons on the outer shell. Due to this fact, atoms may not remain stable all the time. | The formation of molecules takes place to attain stability. |
| Reactivity | Atoms of every element portray a certain degree of reactivity, except the noble elements. | Compared to atoms, molecules are less reactive. |
| Example | Oxygen – O | Water – H2O |
| Hydrogen – H | Phosphorus – P4 |
What is Atom?
When you talk about an atom refers to the smallest particle in any ordinary matter that forms a chemical element. The air around you, anything liquid and solid comprises either ionized or neutral atoms.
The normal size of an atom is around 100 picometers, which is approximately 1 in a millionth part of a millimetre.
Due to the extremely small size of atoms, it is not a simple task to predict their conduct with the help of classical physics. To predict and explain the behaviour of atoms, experts use quantum principles.
You will find a nucleus in every atom, along with a minimum of one electron that will be bound with the nucleus. In turn, this nucleus is comprised of a minimum of one proton and multiple neutrons.
The protons and the neutrons are collectively known as the nucleons, and about 99.94% of the total mass of an atom is present in the nucleus.
The protons in an atom give out positive charges, and the electrons give out negative charges. On the other hand, the neutrons have no charge at all.
What is Molecule?
When a minimum of two atoms are bound together with the help of chemical bonds, it forms a molecule which is electrically neutral by nature. Most of you may argue that molecules are ions that are almost similar to each other.
Well, there is a major difference between the two. Ions are electrically charged, whereas molecules are electrically neutral.
You will notice that molecules are not strictly used in organic chemistry, biochemistry, and quantum physics.
You need to remember that molecules may often be homonuclear. This means that a molecule may contain atoms from a single chemical element.
The best example of this is Oxygen or O2. It may also be heteronuclear, which means that it may contain atoms from different elements, such as water or H2O.
Make a note of the fact that atoms that are connected by any non-covalent interactions are not normally considered as one molecule. An example of this would be ionic bonds or hydrogen bonds.
Main Differences Between Atom and Molecule
- An atom is the smallest particle of any element, whereas a molecule is formed when two or more atoms are held together with the help of a chemical bond.
- It is possible for atoms to either exist or not exist independently. However, molecules always exist independently or in a free state.
- It is not possible to break down atoms any further. On the other hand, molecules can be broken down into atoms of either similar or different elements.
- The nucleus, comprising neutrons and protons, along with electrons, forms an atom. On the other hand, molecules comprise a minimum of two atoms that may either be identical or different and held together by a chemical bond.
- Atoms are always shaped spherical ad molecules that may be angular, rectangular, or linear.
- Atoms happen to be highly reactive. They can easily participate in any chemical reaction and do not decompose further into any subatomic particles. However, molecules are comparatively less reactive and do not participate in chemical reactions.
- https://pubs.acs.org/doi/abs/10.1021/j100154a006
- https://aip.scitation.org/doi/abs/10.1063/1.1681085
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
