[Chemistry Class Notes] on Difference Between Atom and Molecule Pdf for Exam

Everything in this world is made out of some kind of matter. This matter is further divided into smaller parts; they are not visible to the naked eye and can only be observed through instruments specially created to see them. 

Now, what is matter subdivided into? 

The matter is made out of molecules. Be it, Liquids, gases, or solids, they are all made out of molecules. 

Now, molecules are further classified into smaller parts called atoms. 

Confused?

Read on further to know the difference between molecules and atoms.

 

Definition  

Molecule  

Molecules are usually made up of two or more smaller structures called atoms. These atoms share electrons or exchange electrons in order to be held together. The bonding takes place between the particles in the outer shell of an atom.

A molecule is said to be the smallest unit of a chemical compound. It exhibits similar properties as of that of the compound it is a part of. They vary significantly in complexity and size. Everything in this world is made up of molecules, right from the oxygen that we breathe to the furniture we use. 

Some examples of Molecules are O₂ and H₂, Chlorine molecules Cl₂ and others in nature.

 

Atom 

An atom it the smallest part of an element. It shows chemical properties that relate to the element it is forming. Although it is very small in nature, scientists have discovered that atoms can be broken down into smaller parts. They are protons, neutrons, and electrons. An atom of the element always contains a fixed amount of electrons, protons, and neutrons. For example, let’s take the atom of carbon. It has 6 protons, 6 electrons, and six neutrons. Some elements also have something called isotopes, such as carbon. The isotopes of carbon differ in the number of neutrons. This usually results in radioactivity.

Everything in this universe is made of tiny particles called atoms. Believe it or not, there are 92 different kinds of atoms in nature! These 92 different forms combine with one another to form different types of matter that we see all around us in our day to day life.

 

Components 

Molecule

You must be wondering, how molecules are held together? It is because of the shared electron pairs, or more commonly called as covalent bonds. These bonds are directionless and are kept in positions in such a way, that it maximizes bond strength. Because of this, molecules have a definite and rigid structure. It comprises of two or more identical or sometimes different atoms that are chemically bonded together.

 

Atom 

Atoms consist of a nucleus, electrons, neutrons, and protons. The nucleus of an atom holds the majority of the mass of the atom. It composes of protons and neutrons which are totally referred to as nucleons. The lighter electrons orbit the atom’s nucleus. The total sum of protons and neutrons that comprise the atom’s nucleus is called the atom’s mass number which is usually referred to as nucleon number.

 

Protons

Protons are the positively charged particles which are present in the atom’s nucleus. It comprises of the total mass of the atom along with the neutrons. 

 

Neutrons 

These are particles that showcase a neutral charge; they share the nucleus of an atom with protons. The number of protons in each element is a constant number while the number of neutrons can vary. Because of this reason, the element’s mass number can differ from one atom to another. 

 

Electrons

These particles are negatively charged particles that orbit the nucleus of an atom. They are much lighter than both the protons and neutrons and consist of a relative mass of 1/1836 the mass of the protons. Energy levels are referred to the area that the electrons orbit in a series of levels. Each level can hold a specific number of electrons, the first orbit is the one closest to the nucleus, and the levels keep going further and further away. Depending upon the total number of electrons will be the number of energy levels in an atom.

 

Bonding 

Molecules

The molecules are bound by something called covalent bonding. It is the interatomic linkage that arises from the sharing of an electron pair between two atoms. This happens due to the electrostatic attraction of their nuclei for similar electrons. A covalent bond is formed when the bonded atoms have lower total energy than that of widely separated atoms.

A single line between the elements indicates that there is a bond between two atoms double lines (=) represent a double bond between two atoms (i.e., involving two electron pairs), and triple lines (≡) indicate a triple bond. 

Covalent bonds are always directional. This means that atoms that are bonded usually prefer only specific structures that are relative to one another; this, in turn, gives molecules definite shapes, as in the angular (bent) structure of the H2O molecule. 

 

Atoms 

The Coulomb forces are the forces between the electrons and the nuclei. It is the force of attraction and repulsion between the particles and the nuclei. The energy formed between the atoms is the sum of all individual forces, and that is why the electrons are located outside the atom and the nucleus in the center. If two atoms come close together, the force formed is that of repulsion.

The interaction energy is defined as the potential energy between the atoms. It is always negative if the atoms are bound and positive if they can move away from each other. 

The interaction energy is usually minimum at the equilibrium position. This energy value is called the bond energy, and it is the energy needed to separate completely to infinity. This value is defined as the bond energy of the atom. The stronger the bond energy, the harder it is to move the atoms; for example, it is harder to melt solids than to evaporate the liquid. This is because of the bond energy. 

 

Conclusion

Both atoms and molecules are what makes up this entire universe. As mentioned earlier in this article, atoms make up molecules. But, the chemical properties of atoms are not usually retained when they form molecules. The best example is salt. It contains Na which is a highly reactive metal and Cl which is a toxic gas. But when they come together in the necessary proportions, they form table salt (NaCl) which is neither a metal nor toxic. This clearly proves that the chemical properties of atoms are changed when they form molecules.

Molecules can always be separated into their constituent atoms by chemical methods that have been discovered by various scientists. However, this is not possible with atoms. Atoms can be further divided into subatomic particles by means of nuclear methods. 

Molecules can exist independently and are often stable. However, atoms cannot be independent. Only noble gas configurations are able to stabilize by themselves. Argon, helium, krypton are examples of noble gases. The reason behind their stability is that they have reached the maximum number of electrons in their outer shells. Hence, they don’t display any charge. Though, atoms which don’t have this kind of stability come together to either share or relocate electrons to make molecules and to develop into a stable one.