What Is A Molecule?

Though textbook definitions of the word “molecule” can sometimes seem a bit complicated, a molecule can be loosely thought of as a group of atoms stuck together – usually through chemical bonds.

Here we see a single hydrogen atom traveling through the cosmos. It’s made of one positively charged proton in its nucleus, and one negatively charged electron.

If our lone hydrogen atom happens to pass close enough to another lone hydrogen atom, their electrons (which are attracted like magnets to protons) can pull the atoms toward each other until they collide and stick together

The two atoms now share each other’s electrons in what is called a covalent chemical bond.

What were once 2 individual hydrogen atoms have now formed a single hydrogen molecule!

This bond is not permanent. With enough heat or due to interactions with other molecules, the hydrogen atoms will readily separate once more.

Different types of atoms can form different numbers of chemical bonds:

A hydrogen atom can only form one covalent bond at a time. If a 3rd hydrogen were to collide with a hydrogen molecule, it would simply bounce off or, if it hits hard enough or in just the right place, it can trade spots with one of the existing atoms.

An oxygen atom can typically make 2 bonds, a carbon atom can make 4, an argon atom won’t usually bond with anything.

Even though possible bond numbers per atom are small, huge molecules can form if bonds happen to be properly arranged.

For example, even though hydrogen can only form a single bond, a standard water molecule is always made of 3 atoms. This is possible because oxygen, which can form 2 bonds, forms just one bond with each hydrogen atom.

A single molecule of the sugar known as, glucose, is made of 24 atoms, a special arrangement of carbons, hydrogens and oxygens.

A typical fatty acid in the human body may vary in length, this one here is made of 38 atoms.

And a single protein (depending on the type) can contain over half a million atoms, all covalently bound together.

The models I’ve been showing you so far here are what we call “space filling” models. They show us roughly what the outside of each atom’s electron cloud looks like, and different types of atoms have been assigned different colors.

When we look at real molecules with a scanning tunneling microscope, they look pretty similar to these space filling models, but the atoms are not color coded, and their edges are fuzzy. That blur is partly due to the microscope’s limitations and partly because atoms actually do have soft boundaries.

When looking at complex molecules, space filling models and especially, actual images of real molecules, can be a bit confusing. Which atoms are bound together, which atoms are just close to one another?

For this reason, chemists sometimes use what are called ball and stick models. These highlight the bonds between atoms, the skeleton of a molecule, instead of showing each atom’s outside surface.

In 2009, Dr Leo Gross and his team, discovered a way to take actual skeletal pictures of molecules.

This is not a drawing, this is not a computer generated model, this is an actual scan of a real molecule!

Amazingly, atomic theory was allowing scientists to draw molecules with surprising accuracy, over 100 years before this image was finally taken. That’s quite a testament to what a good scientific theory can do.

When atoms come together to form a molecule, the molecule vibrates between its bonds in a regular pattern. You can think of the bond as a bouncing spring. This is because the protons in the nucleus of each atom repel one another, while the shared electrons in each bond pull the atoms back together. The vibrations we find in molecules are the result of a perpetual tug of war between these two forces.

If you add energy to a molecule with heat or light, the amplitude (the length) of each vibration, will increase without changing how frequently each vibration completes its cycle. The “bouncing spring” stretches further, and the atoms move faster. If you add enough energy, the bond will break.

Scientists are fascinated with molecular movements and want to understand them better. These vibrations have a huge number of potential applications in chemistry, medicine, electronics, and computer engineering.

Watchmakers, for example, use the unchanging speed of molecular vibrations to build watches that keep nearly perfect time. In a quartz crystal, bond vibrations between its atoms resonate, causing the entire crystal, when cut to the right shape and size, to oscillate, microscopically, at 32,768 times per second. Inside each quartz watch is a tiny crystal along with electronics that can count the crystal’s vibrations, telling the second hand precisely when to move.

In April, 2019, in the journal, Nature, Joonhee Lee and his colleagues from the center for Chemistry at the Space Time limit, have published the first images ever taken of molecular vibrations at the atomic scale.

Though these images may seem a bit strange to the untrained eye, they show researchers exactly how this molecule bends and pulses between its its bonds. We can use images like this to build accurate models predicting exactly how different molecules will behave under various conditions.

With this new precision knowledge, engineers are working on solar panels that generate far more energy, computer chips that don’t overheat, and researchers are planning to use this imaging technology to better understand our own DNA.

Even in a scientific field as thoroughly studied as chemistry, the old saying is still true: Somewhere, something incredible is waiting to be known!

So in summary, what is a molecule?

A molecule can be thought of as a group of atoms stuck together through chemical bonds.

Different types of atoms can form different numbers of bonds.

Molecules can be as small as 2 atoms stuck together, or as is the case for some proteins, can contain millions of atoms covalently bound.

Recent advances in molecular imaging are now letting us take snapshots of molecular vibrations.

I’m jon Perry and that is molecules stated clearly