# Introduction, chemical symbols and chemical formulae

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## Introduction

As we have already mentioned, a number of changes can occur when elements react with one another. These changes may either be physical or chemical . One way of representing these changes is through balanced chemical equations . A chemical equation describes a chemical reaction by using symbols for the elements involved. For example, if we look at the reaction between iron (Fe) and sulphur (S) to form iron sulphide (FeS), we could represent these changes either in words or using chemical symbols:

iron + sulphur $\to$ iron sulphide

or

Fe $+$ S $\to$ FeS

Another example would be:

ammonia + oxygen $\to$ nitric oxide + water

or

4NH 3 $+$ 5O 2 $\to$ 4NO $+$ 6H 2 O

Compounds on the left of the arrow are called the reactants and these are needed for the reaction to take place. In this equation, the reactants are ammonia and oxygen. The compounds on the right are called the products and these are what is formed from the reaction.

In order to be able to write a balanced chemical equation, there are a number of important things that need to be done:

1. Know the chemical symbols for the elements involved in the reaction
2. Be able to write the chemical formulae for different reactants and products
3. Balance chemical equations by understanding the laws that govern chemical change
4. Know the state symbols for the equation

We will look at each of these steps separately in the next sections.

## Chemical symbols

It is very important to know the chemical symbols for common elements in the Periodic Table, so that you are able to write chemical equations and to recognise different compounds.

## Revising common chemical symbols

• Write down the chemical symbols and names of all the elements that you know.
• Compare your list with another learner and add any symbols and names that you don't have.
• Spend some time, either in class or at home, learning the symbols for at least the first twenty elements in the periodic table. You should also learn the symbols for other common elements that are not in the first twenty.
• Write a short test for someone else in the class and then exchange tests with them so that you each have the chance to answer one.

## Writing chemical formulae

A chemical formula is a concise way of giving information about the atoms that make up a particular chemical compound. A chemical formula shows each element by its symbol and also showshow many atoms of each element are found in that compound. The number of atoms (if greater than one) is shown as a subscript.

Examples:

CH ${}_{4}$ (methane)

Number of atoms: (1 x carbon) + (4 x hydrogen) = 5 atoms in one methane molecule

H ${}_{2}$ SO ${}_{4}$ (sulphuric acid)

Number of atoms: (2 x hydrogen) + (1 x sulphur) + (4 x oxygen) = 7 atoms in one molecule of sulphuric acid

A chemical formula may also give information about how the atoms are arranged in a molecule if it is written in a particular way. A molecule of ethane, for example, has the chemical formula C ${}_{2}$ H ${}_{6}$ . This formula tells us how many atoms of each element are in the molecule, but doesn't tell us anything about how these atoms are arranged. In fact, each carbon atom in the ethane molecule is bonded to three hydrogen atoms. Another way of writing the formula for ethane is CH ${}_{3}$ CH ${}_{3}$ . The number of atoms of each element has not changed, but this formula gives us more information about how the atoms are arranged in relation to each other.

The slightly tricky part of writing chemical formulae comes when you have to work out the ratio in which the elements combine. For example, you may know that sodium (Na) and chlorine (Cl) react to form sodium chloride, but how do you know that in each molecule of sodium chloride there is only one atom of sodium for every one atom of chlorine? It all comes down to the valency of an atom or group of atoms. Valency is the number of bonds that an element can form with another element. Working out the chemical formulae of chemical compounds using their valency, will be covered in Grade 11. For now, we will use formulae that you already know.

How we are making nano material?
what is a peer
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What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
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Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
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anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
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Introduction about quantum dots in nanotechnology
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absolutely yes
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for teaching engĺish at school how nano technology help us
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Do somebody tell me a best nano engineering book for beginners?
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how can I make nanorobot?
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what is fullerene does it is used to make bukky balls
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fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
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what is the Synthesis, properties,and applications of carbon nano chemistry
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is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
how did you get the value of 2000N.What calculations are needed to arrive at it
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