We use cookies to give you the best experience possible. By continuing we’ll assume you’re on board with our cookie policy

Semiconductors, Superconductors, Oxidation States Essay Sample

essay
  • Pages: 3
  • Word count: 582
  • Rewriting Possibility: 99% (excellent)
  • Category: chemistry

Get Full Essay

Get access to this section to get all help you need with your essay and educational issues.

Get Access

Introduction of TOPIC

The oxidation state or oxidation number, is a value assigned to a chemical species which represents its actual or nominal electrical charge.

The oxidation number in a free or uncombined element is zero. This means that, metallic magnesium has an oxidation number of zero, and chlorine in Cl2 form has an oxidation state of zero.

For simple ionic compounds, the oxidation state of the single atom ions is simply the charge on the ions.

In most compounds the oxidation number for hydrogen is +1 and for oxygen is -2. The exceptions include the hydrides (the oxidation state is -1) and the peroxides (the oxidation state for oxygen is -1).

In the compounds, halides usually have the oxidation number -1.

The sum of all the oxidation numbers in a compound have to be equal to zero.

The sum of all the oxidation states in a complex ion is the same as the charge on the ion.

Semiconductors

A covalent element such as silicon or germanium which has a higher conductivity than that of a typical non-metal but a much lower conductivity than that of a metal is desc

ribed as a semiconductor. Semiconductors are also referred to as

Sorry, but full essay samples are available only for registered users

Choose a Membership Plan
metalloids and they occur at the division between metals and non-metals in the Periodic Table.

Key facts : 1. The electrical conductivity of semiconductors increases with increasing temperature.

2: Doping pure crystals of silicon or germanium with certain other elements produces 2 types of semiconductors: n- type and p-type semiconductors.

The addition of small quantities of certain substances to pure silicon greatly enhance its conductivity and makes possible the construction of electronic devices. This controlled addition of impurities is called ‘doping’.

1. doping pure silicon with phosphorus

or arsenic (group 5 elements)

these elements have 5 valence electrons, a few of the silicon atoms are replaced by P, As atoms — 1 electron is left over after the 4 bonds have been formed. The extra electron is free to conduct an electric current and the phosphorus-doped silicon becomes a conductor called n-type.

B. doping with boron or aluminium (group 3 elements). By doping with an element having 3 valence electrons some of the silicon atoms are replaced by boron atoms, but because each boron has only 3 electrons, one of the four bonds to each boron atom has only 1 electron in it. We can think of this as a vacancy or hole in the bonding orbital. An electron from a neighbouring atom can move in to occupy this vacancy. As a result of this movement this type of conductor is called p-type.

Superconductors

1. Superconductors are a special class of materials that have zero electrical resistance at temperatures near absolute zero.

2. Achieving temperatures near absolute zero is difficult and costly so application of superconduction at these temperatures is impractical.

3. Recently superconductors have been discovered which have zero resistance up to temperatures above the boiling point of liquid nitrogen- temperatures which are less costly to attain.

We can write a custom essay on

Semiconductors, Superconductors, Oxidation States ...
According to Your Specific Requirements.

Order an essay

You May Also Find These Documents Helpful

Inorganic Chemistry

Transition elements contain ions that present in aqueous solution as complex ions. A metal ion with a molecule called a ligand are called complex ion and it attached through coordinate covalent bonds. A complex salt is an ionic compound but it differs in the fact that there are these covalent bonds attaching the metal to the ligand. For example in iron(II) ion, it exists in water as Fe(H2O)62+. In this ion, water molecules are arranged about the iron atom with their oxygen atoms bonded to the metal by donating electron pairs to it. A coordination compound is a compound that have either of complex ions and other ions of a neutral species or opposite charge. As an example of coordination compound is the compound K4[Fe(CN)6] which contains the complex ion Fe(CN)6 4- and four K+ ions. Some of the transition elements have biological activity and their role in human nutrition...

General chemistry - Titration

Introduction Titration is defined as technique whereby one solution of accurately known concentration also known as the titrant is added slowly into another solution of unknown concentration until a neutralization reaction is reached. There are several types of titration methods in chemistry. Firstly, is the acid-base titration method which was carried out during this experiment. In an acid-base titration, the acid/base with a known concentration and fixed volume will be added into the conical flask with a pipette and this would be the solution that is to be titrated. This solution is also known as the titrand. The base/acid with a known concentration but no fixed volume would then be added into the burette. This solution is called the titrant [1]. The point where neutralization is reached is usually indicated by an indicator while in some reactions the solutions are self-indicating. Hence, a small amount of acid-base indicator will be...

Ammonium hydroxide solution

In the strong acid-weak base titration, 0. 1 M ammonium hydroxide ( NH4OH ) was titrated with 0. 1 M hydrochloric acid ( HCl ). 2-3 drops of phenolphthalein were added as indicator into the conical flask which contains 25mL of hydrochloric acid. Ammonium hydroxide was then titrated slowly into the conical flask and the conical flask was swirled gently to ensure the reaction is reacted completely. The titration stops when the colour of the titrand changed from colourless to pale pink. The average titrant (29. 55 mL) of 0. 1 M of ammonium hydroxide was added into the conical flask. By using screened methyl orange as indicator, the average titrant (26. 45 mL) of 0. 1 M of ammonium hydroxide was added to change the colour of the titrand from red to grey in conical flask. In weak acid-strong base titration, 0. 1 M sodium hydroxide ( NaOH )...

Popular Essays

logo

Emma Taylor

online

Hi there!
Would you like to get such a paper?
How about getting a customized one?