Atoms, ions and molecules

Published by Daniel Ozori on


We’ve certainly all heard of the word atom, whether it’s from a movie or a friend or even in school, we’re all familiar with word but yet most people still don’t know what it is or why it even exists.

In this article i’ll be giving you the basic knowledge on everything you need to know about the atom.


An atom is the smallest part of an element that can ever exist an still possess the chemical properties of that element.

They are the basic building blocks of ordinary matter and possess the ability to join together to form molecules which makes basically everything you see around you.

Yet still, though the atom is the basic building block of matter, it still contains smaller fundamental particles called protons, electrons and neutrons.

The protons carry the positive electric charge of the atoms, the electrons carry the negative charge, and the neutrons carry no charge at all.

Structure of an atom

The protons and the neutrons cluster together  in the central part of the atoms called the nucleus, and the electrons orbit the nucleus due to the pull of the different charges emitted between them.

Who discovered the atom?

Democritus was the one who originally introduced the atom, but it was John Dalton (1766-1844) an English chemist who proposed the atomic theory.

it states that “all matter is composed of atoms, indivisible and indestructible building blocks, while atoms of the same elements were identical, different elements of different size and mass”.

This theory originated from Dalton’s earlier studies of the properties of atmospheric gases, He observed that water absorbed different gases in different proportions, during his experiments he found out that water absorbed carbon (ii) dioxide better than it absorbed nitrogen.

He hypothesized that it was due to the difference in the mass of the two gases, and proposed that each chemical element is composed of atoms of a different type, and though they cannot be destroyed they can combine to form much more complex structures.

But as result of new discoveries Dalton’s atomic theory has undergone several implications.

Ions– Definition

Some substances are not built up of atoms or molecules, but are made up of charged particles called ions.

An ion is defined as an atom or molecule that has gained or lost one or more of its valence electrons, giving it a net positive or negative electrical charge.

There are two types of ions; the positive charged ions ( cations ) and the negative charged ( anions ).

The positive ions are created when an atom loses an electron and since atoms usually have an equal amount of protons ( positive charge ) and electrons ( negative charge ) and giving the fact that it just lost an electron, it thereby acquires a net positive charge.

They are mainly metals and have the plus sign ( + ) attached to their chemical formula.

Examples of positive ions are; Aluminium ( Al 3+ ), Calcium ( Ca 2+ ) , Zinc ( 2+ ) , Sodium ( Na + ).

The negative ions on the other hand are created when the atom gains extra electrons, surpassing the amount of protons present, it then gains a net negative charge. it is represented by attaching the minus sign ( – ) to the chemical formula of the atom.

Examples of negative ions are; Chloride ( Cl- ), Flouride ( F- ), Oxide ( O- ), Nitride ( N- ).

(If the chemical formula possesses just a minus ( – ) or plus ( + ) sign it just means -1 and +1 respectively)

Polyatomic cations and anions

When an ion consists of two or more atoms it is referred to as a polyatomic ion and it can gain and lose just electrons too just as normal single ions can.

Polyatomic cations are formed when ions with multiple atoms lose electrons and then acquire a positive net charge due to the imbalance. An example of a polyatomic cation is Ammonium ( NH4 + ).

polyatomic anions are formed when ions with multiple atoms gain electrons and acquire a net negative charge. Examples are; Chlorate ( ClO3- ) , Cyanide ( CN- ), Chromate ( CrO4 2- ) and much others more.

Molecules– Definition

At times atoms cannot exist alone, they generally  bond with other atoms to form molecules. Molecules may be made-up of atoms of the same element or of different elements.

Most compounds exists as molecules. The smallest particle possessing the chemical properties of a given compound is its molecule.

A molecule is defined as the smallest particle of a substance that can normally exist alone and still retain the chemical properties of that substance.

To understand how atoms bond to form molecules please use the link to refer to my article on Chemical bonding.

Fun fact; There are over 7×1027 atoms in the human body, that’s just saying seven billion billion billion atoms in a body of mass 70kg.





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