Chemistry is the study of matter

All matter is made of atoms. Atoms are made of a heavy nucleus of protons and neutrons, surrounded by electrons whizzing around it.


The chemical properties of any material depend on its electrons.

Understand what the electrons are doing and you understand Chemistry.



First some definitions



Atoms are the smallest particle of an element. Every element has its own type of atom. All the atoms of any one element all have the same number of positive charged protons in the central nucleus.


Molecules are made when atoms join together.


Ions are atoms or molecules that have a charge because they have either gained or lost negatively charged electrons.


There are three categories into which all materials must fit


Elements – All the atoms have the same number of protons, may be made of atoms or molecules formed by the pairing up of two atoms that are the same.

Compounds – Made by reacting different elements together. Compounds contain at least two elements, chemically joined together

Mixtures – Contain at least two elements or compounds, put together but not chemically joined together, you can separate a mixture very easily.

The Periodic Table



There are 93 naturally occurring elements and another 13 or so that have been made artificially. The elements have been arranged in the Periodic Table based on the work of many scientists, including Dmitri Mendeleev, John Newlands and Henry Moseley.



The Periodic Table is at the heart of an understanding of Chemistry. It arranges elements according to their electron arrangement because an element's chemical properties depend on its electron arrangement. You can download different versions of the Periodic Table without charge by clicking here.


Electrons are arranged in successive energy levels, which get gradually further away from the atom's heavy nucleus of protons and neutrons.


The rows of the Periodic Table are called Periods. Moving left to right across any one period the elements are gradually filling the same electron energy level. Each period represents the filling of another electron energy level.


In Group 1, the left hand column, all the elements have one electron in the highest, outermost, energy level. Group 2 all have two electrons in the highest energy level, Group 3… until Group 0, the last group on the right. These elements have a Full highest energy level.

Why do Elements React?


Atoms react so that they achieve a more stable electron arrangement, one that is less stressed. Group 0 elements have a full highest energy level and cannot become any more stable, so they do not react at all. Other elements gain an electron arrangement approaching that of Group 0 elements by reacting.



Two different kinds of chemical bonds occur


If two non-metallic elements are reacted together, they share their electrons, forming a molecule with a new more stable electron arrangement than either element had before the reaction. This type of bonding is called Covalent Bonding.


If a metal reacts with a non-metal, a different kind of bonding called ionic bonding occurs. Metal atoms become more stable by losing electrons. Electrons are negative though, so the metal atom becomes a positively charged Ion. Non-metals become more stable by gaining negatively charged electrons to form negatively charged Ions.


In a solid these positive and negative ions are fixed in a regular array, with positive ions surrounding each negative ion and vice versa. If the ionic compound is melted the ions can move about independently.

Metals and Non-Metals



Non-metals are all found in the top right hand corner of the Periodic Table. Most elements are solid metals. There are a few peculiarities, like mercury, which is a liquid metal.


There is a block of metals in the Periodic Table situated between Group 2 and Group 3 called the Transition Metals. The Transition metals are usually better electrical conductors than other metals. The chemistry of these metals' compounds is particularly interesting because they are usually coloured.


Copper sulfate has blue crystals, Iron II sulfate is pale green and potassium Manganate VII is dark purple. Transition metals and their compounds are also used in industry as catalysts. A catalyst makes reactions that would otherwise require high temperatures work at much lower temperatures. Modern chemistry is highly dependent on catalysts to keep energy costs down.


Catalysts are used in car exhausts where they make the pollutant gases carbon monoxide and nitrogen monoxide react with each other, to form the harmless gas nitrogen and less harmful carbon dioxide.


Chemistry is divided into three main branches

  • Organic Chemistry – The chemistry of Carbon based compounds
  • Inorganic Chemistry – The chemistry of all the other elements' compounds
  • Physical Chemistry – The study of chemical energy and how it causes reactions to occur


It might seem illogical for one whole branch of chemistry out of only three to be concerned with the study of Carbon compounds, but carbon has the unique ability to form long chain molecules because it can bond with four other atoms. There are more carbon compounds than there are compounds of all the other elements put together.

What Use is Chemistry?


Chemistry has given us new materials, like plastics and synthetic polymers, like stainless steel and paracetamol, like synthetic rubber and glasses. Chemistry gives our scientists the knowledge that allows us to take natural resources as diverse as air, water, iron ore and crude oil and turn them into the oxygen, neon, steel, gas, polythene and dyes that our society needs.


Bronze age chemistry gave us make bronze by heating malachite, copper ore, with cassiterite, tin ore.

Iron age chemistry led to the extraction of metallic iron by heating the iron ore haematite with charcoal.

Modern chemical studies has led to the synthesis of ammonia, which is used to make fertilisers, as well as the extraction of metals like titanium and tungsten.


Biochemistry is the study of chemistry in biological systems and its study forms the basis of medical courses, pharmaceuticals and genetics. This branch of chemistry is where the growth has been over the past few years and where it is expected to be for the next decade.


Metallurgy is a branch of chemistry that draws on an understanding of the electron structures of metals, relating this to the physical properties like tensile strength of metals and their alloys. An alloy is a metal/metal mixture made by mixing molten metals together.


Chemical engineering is the application of engineering principles to chemistry and the bulk production of chemicals. It is chemical engineering that gives us oil refineries, sulphuric acid manufacturing plant and fertiliser factories.