What is the size of the molecules? What are the dimensions of the molecule?

When two or more atoms enter into chemical bonds with each other, molecules appear. It does not matter whether these atoms are the same, or they differ from each other in both form and size. We'll figure out what the size of the molecules is and what it depends on.

What are molecules?

For millennia, scientists have speculated about the mystery of life, about what exactly happens when it is born. According to the most ancient cultures, life and everything in this world consists of the basic elements of nature - earth, air, wind, water and fire. However, over time, many philosophers began to put forward the idea that all things consist of tiny, indivisible things that can not be created and destroyed.

However, it was only after the appearance of the atomic theory and modern chemistry that scientists began to postulate that the particles taken in aggregate gave birth to the basic building blocks of all things. So there was a term that, in the context of modern particle theory, refers to the smallest units of mass.

By its classical definition, a molecule is the smallest particle of a substance that helps maintain its chemical and physical properties. It consists of two or more atoms, as well as groups of identical or different atoms held together by chemical forces.

What is the size of the molecules? In the 5th grade, natural history (a school subject) gives only a general idea of the dimensions and forms, and this question is studied in more detail in the senior classes at chemistry lessons.

Examples of molecules

Molecules can be simple or complex. Here are some examples:

• H ₂ O (water);
• N ₂ (nitrogen);
• O ₃ (ozone);
• CaO (calcium oxide);
• C ₆ H ₁₂ O ₆ (glucose).

Molecules consisting of two or more elements are called compounds. So, water, calcium oxide and glucose are compound. Not all compounds are molecules, but all molecules are compounds. How big can they be? What is the size of the molecule? Known is the fact that almost everything around us consists of atoms (except light and sound). Their total weight and will be the mass of the molecule.

Molecular mass

Speaking about the size of molecules, most scientists are repelled by the molecular weight. This is the total weight of all atoms entering into it:

• Water, consisting of two hydrogen atoms (having one unit of atomic mass) and one oxygen atom (16 units of atomic mass), has a molecular weight of 18 (more precisely, 18,01528).
• Glucose has a molecular weight of 180.
• DNA, which is very long, can have a molecular mass that is about 1010 (the approximate weight of one human chromosome).

Measurement in nanometers

In addition to the mass, we can also measure what the size of the molecules is in nanometers. The unit of water is about 0.27 Nm across. DNA reaches 2 Nm in diameter and can be stretched to several meters in length. It is hard to imagine how such dimensions can fit in one cell. The ratio of length and thickness of DNA is surprising. It is 1/100 000 000, it's like human hair with a length in the football field.

Forms and sizes

What is the size of the molecules? They come in different shapes and sizes. Water and carbon dioxide are one of the smallest, and proteins are among the largest. Molecules are elements made up of atoms that are connected to each other. Understanding the appearance of molecules is traditionally part of chemistry. In addition to their incomprehensibly strange chemical behavior, one of the important characteristics of molecules is their size.

Where can knowledge of the magnitude of the molecules be particularly useful? The answer to this and many other questions helps in the field of nanotechnology, since the concept of nanorobots and intelligent materials necessarily deals with the effects of molecular sizes and shapes.

What is the size of the molecules?

In the 5th grade, natural science on this topic gives only general information that all molecules consist of atoms that are in constant random motion. In the upper grades one can already see structural formulas in chemistry textbooks that resemble the actual form of molecules. However, it is impossible to measure their length with a conventional ruler, and in order to do this, you need to know that the molecules are three-dimensional objects. Their image on paper is a projection onto a two-dimensional plane. The length of the molecule changes with the help of the links of the lengths of its angles. There are three main ones:

• The angle of the tetrahedron is 109 °, when all the bonds of this atom with all other atoms are single (only one dash).
• The angle of the hexagon is 120 °, when one atom has one double bond with another atom.
• The angle of the line is 180 °, when the atom has either two double bonds or one triple bond with another atom.

Real angles often differ from these angles, since it is necessary to take into account a variety of various effects, including electrostatic interactions.

How to imagine the size of molecules: examples

What is the size of the molecules? In grade 5, the answers to this question, as we have already said, are of a general nature. Schoolchildren know that the size of the named compounds is very small. For example, if you turn a molecule of sand in one single grain of sand into a whole grain of sand, then under the resulting mass you could hide the house in five floors. What is the size of the molecules? The short answer, which is also more scientific, has the following form.

Molecular weight is equated to the ratio of the mass of the whole substance to the number of molecules in the substance or the molar mass ratio to the Avogadro constant. The unit of measurement is kilogram. The average molecular weight is 10 ^-23 -10 ^-26 kg. Take, for example, water. Its molecular weight will be 3 × 10 ^-26 kg.

How does the size of a molecule affect the forces of attraction?

Responsible for the attraction between molecules is the electromagnetic force, which manifests itself through the attraction of opposites and the repulsion of similar charges. The electrostatic force that exists between opposing charges dominates in interactions between atoms and between molecules. The gravitational force is so small in this case that it can be neglected.

In this case, the size of the molecule affects the force of attraction through the electronic cloud of random distortions that arise when the electrons of the molecule are distributed. In the case of nonpolar particles exhibiting only weak van der Waals interactions or dispersion forces, the size of the molecules has a direct effect on the magnitude of the electron cloud surrounding this molecule. The larger it is, the greater the charged field that surrounds it.

A larger electron cloud means that more electronic interactions can occur between neighboring molecules. As a result, one part of the molecule develops a temporary positive partial charge, and the other - a negative one. When this happens, the molecule can polarize the electron cloud from the neighboring cloud. Attraction occurs because the partial positive side of one molecule is attracted to the partial negative side of the other.

Conclusion

So, what is the size of the molecules? In natural history, as we found out, one can only find a figurative idea of the mass and dimensions of these tiny particles. But we know that there are simple and complex connections. And to the second you can include such a thing as a macromolecule. This is a very large unit, for example a protein, which is usually created by polymerization of smaller subunits (monomers). They usually consist of thousands of atoms or more.

The most common macromolecules in biochemistry are biopolymers (nucleic acids, proteins, carbohydrates and polyphenols) and large non-polymeric molecules (such as lipids). Synthetic macromolecules include conventional plastics and synthetic fibers, as well as experimental materials such as carbon nanotubes.