about ionic bond and covalent bond

the bonding of the compound is determined by its electron arrangement

covalent bond
- elecrons sharing between its atoms within a molecule (the structure is hold by weak intermolecular force)
ionic bond
- formed by ions (the structure is hold by strong electrostatics force between cations and anions)
metallic bond
- bonds between metal atoms (the structure is hold by strong electrostatics force between nucleus and electons of the metallic atoms)

Ionic, Covalent

Ionic and Covalent Bonds are two different types of bonds that are seen in molecules. Both involve electrons. Atoms are able to achieve stability in their valence electrons through the interaction with other atoms. But how they do this can differ.

Covalent bond:
-non-metal + non-metal
-bond in which one or more pairs of electrons are shared by two atoms.

Ionic bond:
-metal + non-metal
- bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other.

In the case of an ionic bond, an electron is simply transferred to another atom. By doing so, each atom is able to have a stable valence shell. It is called an ionic bond because the atoms become ions, a charged atom that has either lost an electron (negative charge) or has extra electrons (positive charge). Below is an animation of ionic bonding:

In the case of sodium chloride, an electron from the sodium is transferred over to the chlorine atom. This enables the sodium atom to be stable, as it doesn’t have any electrons in its valence shell, and the chlorine is stable as well, as it has a full valence shell.

Covalent bonds are a bit different. Rather than transferring an electron over to another atom, the atoms “share” the electron.

In this case, the two chlorine atoms share an electron, enabling them to both achieve a stable valence shell. Sometimes, there is an unequal sharing of the electrons. This is known as Polar Covalent bonds. One note about covalent bonds – they can only occur when two electrons are shared by non-metallic atoms.

If you want to refer to the diagram, you can click into this web site:
http://teachers.pasd.k12.pa.us/hs/plavcand/Ionic%20and%20Covalent%20Bonds.htm

Comparison of Properties of Ionic and Covalent Compounds

Ionic Compounds

Crystalline solids (made of ions)
High melting and boiling points
Conduct electricity when melted
Many soluble in water but not in nonpolar liquid

Covalent Compounds

Gases, liquids, or solids (made of molecules)
Low melting and boiling points
Poor electrical conductors in all phases
Many soluble in nonpolar liquids but not in water

More about each bond under this web site:
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond.html

eg: C2H2 (Ethyne gas) & lead(ll)sulphide & potassium oxide
C2H2 (Ethyne gas) - covalent bond
lead(ll)sulphide - ionic bond
potassium oxide - ionic bond

For Me,I will firstly see whether the compound involved metal or not~
Let's take potassium oxide to be an example~
potassium oxide involved metal(potassium)
so it's bond is ionic bond~


Metallic Bonds

Metallic bonding is the electrostatic attraction between delocalized electrons, called conduction electrons, and the metallic ions within metals. Because it involves the sharing of free electrons among a lattice of positively-charged metal ions, metallic bonding may be compared to that within molten salts.

Metallic bonds are non-polar, because in alloys there is little difference among the electronegativities of the atoms participating in the bonding interaction (and in pure elemental metals, none at all), and the electrons involved in the interaction are delocalized throughout the crystalline structure of the metal.

The properties of metals suggest that their atoms possess strong bonds, yet the ease of conduction of heat and electricity suggest that electrons can move freely in all directions in a metal. The general observations give rise to a picture of "positive ions in a sea of electrons" to describe metallic bonding.

http://en.wikipedia.org/wiki/Metallic_bond