How and Why Atoms Combine - A Look at Ionic, Covalent and Metallic Bonding and their Properties
Posted: Tuesday, May 05, 2009
by Connor Davidson
Firstly, I would advise you read A Brief Look at the Periodic Table of Elements - History, Purpose and Construction before reading this if you have not already. To understand how atoms a combine and why they combine you must first must understand what they are made of
Notice in the diagram that the electron (blue) has a negative sign, the proton (red) has a positive sign and the neutron (green) has no sign. This is referring to its charge. For example one electron can be said as being 1 - and a proton 1 + . Therefore, two electrons could be written as having a charge of 2 - and so on.
The three main types of bonding are shown below:
1. Ionic Bonding
2. Covalent bonding
3. Metallic Bonding
I will go through each individually:
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1. Ionic bonding.
In brief, ionic bonding is the transfer of electrons from one atom to another. It is a bond between metals and non-metals and forms what is called an ionic lattice.
Note: the aim of all atoms is to have the same number of outer electrons as the group 0 (red on table below) which is 8. The number of outer electrons equals the group number (before an element bonding).
To determine how many electrons are gained or lost you need to look at the periodic table below.
Periodic table from Wikipedia
If an element were in groups 1-3 it would lose the same number of electrons as is its group number. Hence becoming positively charged because electrons are negative and you are left with more positive protons than negative electrons.
However, if an element is in groups 5-7 it would take electrons from the ones which we giving them up to become negative - Hence getting 8 outer electrons.
An ionic substance forms into large structures called lattices. As shown below:
On the above diagram the yellows are positive and the blues are negatively charged. They compound stays together as positive is attracted to negative.
Properties
High melting and boiling points
Conducts electricity
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1.Covalent Bonding
Covalent bonding is very different from ionic bonding as it involves only non-metals and is the sharing of electrons as opposed to the transfer of them.
A covalent bond is defined as the sharing of electrons to achieve a stable outer electron arrangement. The bond is held together by the forces of attraction between the positive and negative charges. They are very hard to break and therefore require large amounts of energy to break (1000 KJ mol -1 to be exact)
There are two types of covalent bonding that I will explain separately:
2.1 Covalent molecular
1.2 Covalent network
2.1 The covalent molecular bond is formed between non-metal elements to form compounds. A covalent molecular substance consist of a small molecules joined together by strong covalent bonds and the other molecules in the substance are held together with weak forces called Van Der Waal's (pronounced van-der-val) forces. The diagram below shows this in action in water:
The solid lines between the circles represent the covalent bonds and the dotted lines represent the weak Van Der Waal forces.
Properties
Does not conduct electricity
Very low melting and boiling points
2.2 The covalent molecular molecule is the same except everything is joined by covalent bonds and there are no weak forces involved. They form giant structures. A human is mainly a giant covalent structure of carbon.
Properties
Very high melting and boiling points
Does not conduct electricity (except from carbon in the form of graphite)
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2. Metallic Bonding
Metallic bonding is the sharing of free electrons (delocalised electrons). They form lattice structures very similar to that of ionic compounds.
Properties
Conducts electricity
High Melting and boiling points
Connor Davidson is a UK based writer. He writes on wide variety of topics with his main interest being science, maths and engineering.
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Feel free to reprint these articles on your website by using the reprint button. If you have any questions or comments please post them below - I read all comments.
You can keep up to date with his writings by following him on twitter: https://twitter.com/#!/Connor_Davidson.
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Top-level comments on this article: (2 total)Connor,As my favorite categories to read are science, history, politics, maths and English (Well, I used to teach it at the college level) you've touched a nerve. However, articles like these are a bit beyond the preference of most Warp readers. But as for me? Keep 'em coming. Love the formatting and the graphics. Great attention to detail.Thanks for the comment.
Grat information, you did well at making the details easy to read and understand... thank youThanks for the comment.
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