We often heard the term “molecule” in some chemistry-related topics in school. You can either be one of those students who know the concept of molecules with all your heart or the other way around. Either way, if you’re pursuing a field related to chemistry, knowing the characteristics of molecules is essential.

Atom: The smallest unit of substance

A molecule is considered as the smallest unit of a substance. This is the smallest but still identifiable and dividable part. In a simple scientific definition, molecules are a group of atoms that are being held together by chemical bonds. In its basic form, molecules are electrically neutral. If a molecule has an electrical charge, these molecules are called ion instead. The study of the molecule is called molecular chemistry or molecular physics.

There are two types of molecules based on the number of different chemical atoms within it. A molecule with only one element (like oxygen or O2) is called a homonuclear molecule. Meanwhile, molecules with different atom composition (like water or H2O) are called heteronuclear molecules. Take note: hydrogen bonds and ionic bonds are not single molecules.

What Are The Most Important Molecules In the body?

Thousands of different kinds of molecules make up the human body. Each type of molecule has one specific but critical task. Most of these molecules are essential to the human body that having a deficiency in any of these can be life-threatening.

  • Water- It is made up of one oxygen atom and two hydrogen atoms (H2O) and is one of the most important compounds in the body. A normal adult’s body consists of around 50 to 65% of water.
  • Oxygen – It is a gas that consists of two oxygen atoms (O2) and is responsible for a lot of processes (like cellular respiration).
  • DNA – DNA has a more complex structure than the two previous examples, as it contains a lot of information about humans. It has four bases, namely: adenine, thymine, guanine, and cytosine.
  • Hemoglobin – is a large molecule responsible for ensuring the transport of oxygen to cells.
  • ATP – or adenosine triphosphate, it is responsible for releasing energy which the human body can use. These molecules usually work with hemoglobin and oxygen to ensure that the body can function properly.

10 characteristics of molecules

1. Molecules have definite mass and size

Molecules have definite mass and size due to the same set of atoms.  For example, there is no heavier or smaller Oxygen molecule because each one always consists of two oxygen atom. The size and shape of each oxygen molecule are the same whenever and wherever.

2. New molecules are different than parent molecules’ characteristics.

This characteristic can be applied to heteronuclear molecules. Carbon, hydrogen, and oxygen atoms are different kinds of atoms found in nature. If you combine 12 carbon, 22 hydrogen, and 11 oxygen atoms, in that order (C12H22O11), this will form a sugar molecule. Neither the original atoms and the new molecules have the same characteristics.

3. Changing the atomic distribution will change the molecule.

Even at the slightest modification, a molecule will change if the atomic configuration (or the distribution of atoms inside it) is changed. For example, water (a vital molecule in the human body) is composed of one hydrogen and two oxygen atom. When you add additional hydrogen atom in the mix, it turns into hydrogen peroxide, which is a mild antiseptic.

4. Molecule vs. compound

A compound is a collection of two or more heteronuclear molecules. For example, water is a substance that has billions of H2O molecules and is considered a compound. These molecules are not bonded together. Instead, they keep each other in proximity via attraction.

5. Molecule vs. mixture

A mixture is formed when there is a collection of different molecules and atoms joined together. Only the attraction of molecules is what keeps them together, and not a chemical bond. Unlike a compound, all the molecules and atoms are not the same.

6. Molecule vs. element

An element is a way to describe different classes of atoms. These elements are what makes up different kind of molecules. For example, H2O is a single molecule that comprises hydrogen and oxygen. These two atoms are called elements. Each element has the same physical and chemical properties of other same element atoms.

7. You cannot separate atoms in molecules physically.

Since atoms in a molecule are bonded together chemically, there is no way you can separate the atoms physically. Atoms in a molecule are chemically bonded; hence, these atoms can only be modified by chemical means.

8. A molecule doesn’t have physical properties.

A single molecule doesn’t have any physical properties. This means that you cannot call a single water molecule, a gas, solid, or a liquid. To form physical characteristics, you need to have a group of other molecules.

9. The molecular formula gives basic molecular information.

The molecular formula (or the collection of letters with subscript numbers) gives the basic information of a molecule. This also gives a lot of information about the complexity of the molecule. You will know how many elements are there in a molecule, as well as its atomic composition, just by looking at its name. As of now, the longest molecular formula ever is for Titin, which as a formula, consists of 189,819 letters. Its simplified formula is C169723H270464N45688O52243S912.

10. Molecular polarity depends on the electron density

The polarity of a molecule depends on the number of electrons formed across the atoms inside the molecule. If molecules have high polarity, it means that it is hydrophilic, which will mix well with water and other similar compounds. Polarity can help in deciding what molecules should be mixed to get a particular solvent.