cum
top of page

CSEC Chemistry: Bonding, Allotropes And Isotopes Explained

So, we all know by now that there are tiny bonds holding all of the substances around us together, on the atomic and molecular level.

I aim to help you to understand how these bonds work, are created, and what exactly they do.

This Article will detail the different types of bonds, common carbon allotropes, and their uses, and finally, isotopes and their properties.

------------------------------------------------------------------------------------------------

Bonding

There are 3 types of bonding, ionic, covalent and metallic.

Metallic- Metal and metal

Ionic- Metal and non-metal

Covalent- Non-metal and Non-metal

-------------------------------------------------------------------------------------------------

IONIC BONDING

Ionic bonds occur when a positively charged ion and a negatively charged ion come together as a result of electrostatic attraction.

------------------------------------------------------------------------------------------------



When an atom loses an electron to another atom, it becomes a positive ion.

When an atom gains an electron from another atom, it becomes negative.

We call ionic compounds ionic crystals.

When these ions bond together they have certain characteristics that set them apart from other types of bonds.

The metal forms the first part of the name of the compound and remains unchanged.

The non-metal forms the ending of the compound and the ending is usually changed to 'ide' eg. Calcium and oxygen form calcium oxide.

When polyatomic, the name of the metal and the polyatomic atoms are involved are combined as is. E.g. magnesium sulphate.

----------------------------------------------------------------------------------------

Ionic compounds have certain defining characteristics:

  • High melting point.

  • Hard and brittle.

  • Usually soluble in water.

  • Insoluble in non-polar organic solvents.

  • Melted ionic compounds conduct electricity, and so do ionic compounds dissolved in solutions, but solid ionic compounds do not conduct.

So chances are, if the substance you're reviewing is like this, its an ionic solid!

----------------------------------------------------------------------------------------

COVALENT BONDING

A covalent bond is formed by the sharing of a pair of electrons between two atoms, each atom providing one of the electrons in the shared pair.

Covalent bonds are formed between non-metals

Some atoms even form more than one bond to fill their valence shells.




 

In naming these compounds, the first atom stays the same, while the second atom takes a prefix, depending on the amount of it.

1-Mono

2-Di

3-Tri

4-Tetra

5-Penta

6-Hexa

7-Hepta

8-Octa

Covalent bonds tend to have defining characteristics as well:

  • Low melting points.

  • Soft or brittle solid forms.

  • Poor electrical and thermal conductivity

  • Low boiling points

  • Low density


 

METALLIC BONDING



----------------------------------------------------------------------------------

Metallic bonding occurs between metals.

When metal atoms approach each other, the valence shells overlap and the valence electrons become delocalized. This means that each electron is not associated with a particular atom, but instead moves throughout the structure.

Metallic bonding refers to the attraction force between a sea of delocalized electrons and metal cations.

It can be described as the sharing of electrons among positively charged ions.

-----------------------------------------------------------------------------------

Metallic compound characteristics

-Metallic compounds are malleable and ductile

-Very high melting point and boiling point

-Very good conductors of heat and electricity

-Metallic luster

-Sometimes magnetic

-----------------------------------------------------------------------------------

ALLOTROPES

Allotropes are alternate physical forms of an element, where the bonds between the atoms are shaped differently.

Eg. Graphite and diamond are both technically made of carbon, but the bonds are arranged differently, and in different numbers, forming two completely different chemical structures of the same element, with different properties.

---------------------------------------------------------------------------------



--------------------------------------------------------------------------------

Diamond and graphite are both giant covalent substances made entirely of carbon atoms. Both have chemical formula , but they do not have a molecular formula.

Molecular structure

  • Diamond: Giant covalent structure, with each carbon covalently bonded to four other carbon atoms in a tetrahedral arrangement to form a rigid structure.

  • Graphite: It is also Giant covalent structure, with each carbon covalently bonded to three other carbon atoms in a hexagonal arrangement.

Hardness

  • Diamond: Extremely hard due to rigid, tetrahedral arrangement of carbon atoms.

  • Graphite: Soft. Layers of hexagonally arranged carbon atoms can slide over one another.

Electrical conductivity

  • Diamond: Insulator. Mobile electrons are absent. All four valence electrons are used in covalent bonds.

  • Graphite: Conductor. Three out of four valence electrons are used for covalent bonding with other carbon atoms. Remaining valence electrons can be delocalized across the planes of carbon atoms.

----------------------------------------------------------------------

Diamond is a kind of carbon that takes shape in the crystal system of the greatest symmetry referred to as the cubic system born thousands of miles below the surface area of the earth. Diamonds are created after countless years under heat and great pressure. They are brought to the surface area through a volcanic eruption. A diamond which is naturally created under the earth crust is referred to as Real Diamond.

----------------------------------------------------------------------------

Hardness: Diamond is the hardest mineral found on earth.

Transparency: Diamond is transparent.

Graphite is a non-metal. It is also an allotrope of carbon such as diamond and fullerene. Every layer is only оnе-аtоm-thiсk. It can also conduct electricity as every Carbon is only bonded to three others, leaving the fourth electron free as a delocalized electron.

Molecular Structure: In diamond, the carbon atoms are covalently bonded to one another producing a three-dimensional network solid.

---------------------------------------------------------------------------

Graphite is a non-metal. It is also an allotrope of carbon such as diamond and fullerene. Every layer is only оnе-аtоm-thiсk. It can also conduct electricity as every Carbon is only bonded to three others, leaving the fourth electron free as a delocalized electron.

---------------------------------------------------------------------------

Molecular Structure: Graphite is also made of carbon atoms. Graphite consists of carbon atoms covalently bonded together in a layer made up of hexagons, like chicken wire.

Hardness: Graphite is a soft mineral.

Transparency: Graphite is opaque.

-------------------------------------------------------------------------------------------------



-------------------------------------------------------------------------------------------------

USES OF DIAMOND

Diamond is very popularly known for being used as a gem in jewelry but other than this basic use of diamond there are many other uses of this valuable stone. Diamonds are being used in many industries as well for various operations. Along with being used in the industry, diamonds are also used for some basic general uses.

  1. Glass cutting: Small pieces of diamonds are used for cutting glasses. The small portions of diamonds are also used for drilling the rocks. The hardness of the diamond is the main reason why diamonds are preferred for doing such cutting and drilling activities. You must have also heard that a diamond can cut a diamond and that is true. A small portion of diamond can be used for making a cut in large diamond pieces.

  2. Polishing other stones: No matter if a diamond is used in the solid form or in the form of dust, diamond holds a number of uses. The dust of the diamond can be used for polishing other diamonds and precious stones. The dust of the diamond gives an enhanced shine in the other stones.

  3. Tungsten Wires: It may also amaze some of the people that a diamond can also be used in making tungsten wires. The diamond dies are used for the process of making the wires using the lab equipment.

  4. Engrave Stones: According to the well-known site of Hunker, diamonds can be used for engraving stones to various other metals. The various stones that can be engraved are granite, quartz, etc. The workers feel no need for the replacement of engraving bit as the diamond does not break, scratch or damage any of the stones. As a result of the same, the work can be done without any worries or tension.

  5. Electronic Applications: Since diamonds possess a high level of thermal conductivity, therefore, diamonds can be used in various electronic applications to prevent the delicate parts from getting damaged from the heat rays of the sun. The diamonds are used as heat sinks in such electronic applications for repealing away the heat of the sun.

  6. Lapping: Lapping is also a very popular method which uses diamond. In the process of lapping, a diamond slurry is used. The diamond slurry is made by mixing water with a mixture that contains small pieces of diamonds. This diamond slurry is then applied between the two surfaced that needs to be lapped and rubbed for getting results.

  7. Antidote for Poison/Disease: While there is no scientific evidence backing this usage, diamonds are often used as antidotes in various places for poisons or diseases. The belief that eating diamonds would ward off illness stems from the days of the plague. The lower classes felt the deadly effects of the plague before the upper classes did, a result of their inferior health care and dirtier living conditions. However, many poor people came to the conclusion that it was the diamonds that the wealthy people were swallowing that were keeping them healthy.

  8. Heat Sinks: A heat sink is a component in an electronic system that cools it by eliminating heat and mixing into the surrounding. Diamonds have a high thermal conductivity that means they are very good heat conductors and diamonds are used as a good tool for heat sinks.

-------------------------------------------------------------------------------------------

USES OF GRAPHITE

The important uses of graphite are as follows.

1. The major use of graphite is in making lead pencils of different hardness levels, by mixing it with different proportions of clay. The weakly held layers of carbon atoms in graphite easily slide over each other and are left behind on paper as black marks.

2. Due to its slippery nature, graphite is used as a dry lubricant in machine parts.

3. Being resistant to chemicals and having a high melting point and also because it is a good conductor of heat, graphite is used to make crucibles.

4. The presence of free electrons makes graphite a good conductor of electricity and it is used to make electrodes.

5. Graphite has the ability to absorb fast-moving neutrons, thus, it is used in nuclear reactors to control the speed of the nuclear fission reaction.

Graphite is bonded in many thin layers, bound by weak forces, called Van Der Waals forces. This slipping and sliding of the layers is what makes graphite a great solid lubricant.


-------------------------------------------------------------------------------------------------





-------------------------------------------------------------------------------------------------

ISOTOPES

So now, we come to the interesting world of isotopes, where we will be learning the definition and properties of them.

An isotope is an alternate version of an element, which differs from it, by having a different neutron number.

The neutron number is the amount of neutrons that an atom has in its nucleus.

Every element has at least one isotope, and the mass and relative abundance of the isotope/s is different for each element.

It's kind of like in the animal kingdom, you have several species of ant, all with unique qualities, but at the end of the day, it' s still an ant. So even though we have Uranium-238 and Uranium-235, it's all uranium, just with different neutron numbers, qualities, and abundance.

So we see that isotopes play a very important part in chemistry, as different isotopes of the same element are used for different things.

For example, Uranium-235 and Uranium-238, all uranium, but uses are drastically different.

Uranium-235 only makes up 0.7% of all uranium found world-wide, and it is the isotope most used for weapons and power as it can be used in fission. The more abundant isotope, 238, must be enriched to be able to perform as well as 235.

Another example would be the different isotopes of hydrogen, Hydrogen-1 (protium), Hydrogen-2 (deuterium) and Hydrogen-3 (tritium)

All isotopes of the most abundant element in the universe, so how could they differ?

Hydrogen-1 is the hydrogen we all know and love, it is that vital ingredient of water, and fuels stars, meanwhile, at around 1.1% abundance, we have deuterium, which is used to make heavy water, which is used to cool nuclear reactors, and finally we have tritium, only found in trace amounts, which is radioactive, and could be used as nuclear fuel, but most commonly, used to be used in studying radioactive decay of other elements and their isotopes.

------------------------------------------------------------------------------------------------



------------------------------------------------------------------------------------------------

The reason an isotope is still the same element, even though the neutron number has changed, is that it retains the same proton number, therefore not changing which element it is.

-----------------------------------------------------------------------------------------------



-----------------------------------------------------------------------------------------------

These are the most naturally abundant isotopes of carbon found.

As we can see from the diagram, these are all carbon, but have different qualities, you see, carbon 14, unlike the others, is radioactive, and will decay over a long period of time, it is used in carbon dating. Carbon 12 is what most natural carbon is, it is used as a standard to measure other elements by, as we will see when doing the mole concept, and is found in all living beings, carbon 13 is also found in living beings, albeit in much smaller quantities, and is used to date when rocks were created, and identifying what the source of a body of is.

In conclusion, it is apparent that isotopes are all drastically different, having varying rarity and qualities, but yet being the same element, as the proton count is the same.


709 views0 comments

Recent Posts

See All

CSEC Chemistry: Complete Syllabus Review

Hello Chemistry students! This material was covered in Quelpr's CSEC Chemistry on June 26, 2021, however the past paper questions and solutions have been removed. If you are interested in similar cont

bottom of page