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Inorganic Chemistry

Inorganic Chemistry

Inorganic chemistry relates to chemical reactions for substances which generally do no include carbon.

Introduction

The area is covered in relationship to the periodic table.. Periodic Table   The periodic table arranges all elements in increasing proton number and shows the similarity of elements with related electronic configurations.

For atoms to combine to form compounds they must lose electrons or gain or share electrons.  The electrons lost gained or shared mostly inhabit the outer shell of the atom.  The stable number of electrons in the outer shell is generally eight.  If the outer shell is full of electrons then the atom is stable and does not easily form compounds e.g. Helium, Neon etc.

Note: For notes on Redox (Oxidation - Reduction) refer to Redox Notes..

The periodic table as shown includes the tradition method of identifying the vertical columns (groups) IA to VIIA and IB to VIIB, and 0 for the noble gases.   The periodic table as shown also includes the modern group numbering system 1 to 18.

The horizontal rows are called periods. The top three rows are called short periods. the lower four rows are called long periods and include the transition elements.   Within a period the elements all have the same number of shells.   The shell with increasing numbers of electrons in the outer shell along the columns.

The periodic table identifies a very general overall characteristics : In moving down a group the elements show more metallic characteristics as the atoms size increases: Moving across the table the atoms change from a metallic (electropositive) behaviour to a non-metallic (electronegative ) behaviour.  Thus the most metallic elements are to the bottom left of the table and the most non-metallic tend to be at the top right of the table.

Chemical Characteristic Identifiable from the Periodic Table

Group 0 ( 18): Inert gases.. (filled outer electron shell, stable electron configuration )
Includes Helium, Neon, Argon, Crypton, Xenon and Radon.  All these elements are gases which stable and do not readily react to form compounds. They are generally identified as noble gases. These have eight electrons consisting of four pairs.   Because their valence electrons are all paired up the Noble gases don't normally form bonding associations.   Their valency is therefore considered to be zero.  There are only a handful of compounds formed, mostly with Xenon and Radon.

Group VIIA(col 17): Halogens.. (one electron short of stable structure )
This group includes Fluorine, Bromine, Chorine, Iodine, Astatine**.   Halogens have similar electronic structures to the Inert gases but do not have complete outer shells with one electron being missing.  The halogens are therefore typical non-metals i.e they have high electonegativies-high electron affinities and high ionisation energies.  

Group VIA (16): Beginning with Oxygen the elements have six valence electrons.   These include two sets of paired electrons and two unpaired electrons.    Unpaired electrons are considered excellent candidates for bonding electrons. These elements generally form co-valent bonding when combined with non-metals.   They are said to form di-valent covalent bonding.

Groups VA (15) : Beginning with Nitrogen these elements include five valency electrons with two paired up electrons. The paired electrons are not be candidates for bonding and are referred to as "non-bonding" electrons.   These elements usually form co-valent bonding when combined with other metalloids or non-metals.   They generally are considered tri-valent atoms and form three covalent bonding pairs.

Groups IVA, VA (14) Topped by Carbon and Silicon are considered tetra-valent capable of forming four covalent bonds with other atoms or group of atoms.

Group IIIA (13) Starting with Boron atoms are said to be tri-valent and generally form co-valent bonding associations.

Groups IIIB to IIB (cols 3 to 12): Transition metals (partially filled d electron states, one or two electrons in next shell ).

Groups 2A (cols 2): Alkaline earth metals ( Two electron in excess of stable structure )
These are referred to as di-valent atoms and generally form ionic bonding with non-metals and metalloids.

Groups 1A (cols 1 ): Alkali metals ( One electron in excess of stable structure )
These elements are mono-valent and generally form ionic bonding with non-metals or metalloids.   They form mono-valent bonding because they only have one unpaired electron in their valence region.   Unpaired electrons are excellent candidates as bonding electrons.

Groups IIIA ,IVA, VA (cols 13,14,15) : Intermediate characteristics by virtue of valence electron stucture
Most metal elements are electropositive (capable of donating a few valence electrons )



Relevant Links..
  1. Understanding Chemistry -Inorganic Chemistry Menu ...Chemguide excellent primer notes.
  2. Inorganic Chemistry...Wikipedia free encyclopedia.. Useful notes with donor contributions.
  3. ChemWiki understanding inorganic chemistry... Lots of relevant information
  4. MolData.. INORGANIC CHEMISTR... A website linking to extensive useful chemistry resources

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Last Updated 29/01/2013