FORMATION OF COMPOUNDS

Chemical bond
•Atoms of other elements tend to achieve the stable electron arrangement.
•Can be formed by the transfer of electron or sharing electrons.


Ionic bonds
•Are formed through the transfer of electrons between atoms of metal and non-metal.
•Metal – donate electron / non-metal – accept electron
Formation of ions
•Anion : an atom that accepts electrons forms a negative ion.
•Cation : an atom that donates electrons forms a positive ion.


Example:
Formation of magnesium oxides
The formation of ionic bonds in magnesium oxide, MgO, is explained as follows:
•The electron arrangement of magnesium, Mg, atom is 2.8.2.
•Magnesium, Mg, atom donates its two valence electrons to form magnesium ion.
•Magnesium ion achieve a stable electron arrangement ( octet electron arrangement ).
•Electron arrangement of oxygen is 2.6.
•Oxygen, O, atom receives two electrons to form oxide ion.
•Oxide ion achieves a stable electron arrangement ( octet electron arrangement ).
•Strong electrostatic force pulls the magnesium ion and oxide ion together.
•An ionic bond is formed.

COVALENT BOND

Covalent bond
•The chemical bond formed through the sharing of electrons between two non-metal atoms.
Single bond
•Covalent bond formed when a pair of electron is shared between atoms.
Double bond
•The type of covalent bond formed through the sharing of two pairs of electrons between two non-metal atoms.
Triple bond
•The type of covalent bond formed through the sharing of three pairs of electrons between two non-metal atoms.

example:
THE FORMATION OF TETRACHLOROMETHANE ( SINGLE BOND )

The formation of single covalent bond in tetrachloromethane molecule can be described as follows:
•Each chlorine, Cl, atom has an electron arrangement of 2.8.7 while a carbon, C, atom has electron arrangement of 2.4.
•The outermost shell of chlorine ,Cl, atom and a carbon, C, atom lack one electron and four electron respectively to achieve a stable electron arrangement.
•One carbon, C, atom shares electrons with four chlorine, Cl, atoms.
•Each carbon, C, atom contributes four valence electrons while each chlorine, Cl, atom contributes one valence electron for sharing.
•Each chlorine, Cl, atom achieves the electron arrangement of 2.8.8. Each carbon, C, atom achieves an electron arrangement of 2.8.
•Each atom in the tetrachloromethane molecule achieves a stable electron arrangement.
•Four single covalent bonds are formed.

Characteristic Of Ionic Bond.
Element
•Between metals ( Group 1,2 & 13 ) and non-metal.
Bond formation
•Electron is released by metal atoms and received by non-metal atoms (electron transfer).
Type of particle formed
•Metal – positive ion
•Non-metal – negative ion
How to predict the formula
•Determine the charge of ion.


Characteristic Of Covalent Bond
Element
•Between non-metal and non-metal (Group 14,15, and 16)
Bond formation
•Pairs of electrons are shared by the same or different non-metal atoms.
Type of particle formed
•Neutral molecule
How to predict the formula
•Determine the number of electrons needed to achieve duplet/octet.


The Physical Properties Of Ionic Compound
Melting and boiling points.
•High because positive ion and negative ion are pulled.
•Large amount of energy is needed to overcome it.
Electrical energy.
•Cannot conduct electricity when in solid state but able to conduct electricity in molten or liquid states.
Water solubility
•Most are soluble in water but not in organic solvent
Volatility
•Non-volatile because ion are pulled by strong electrostatic forces.



Physical Properties Of Covalent Compound.
Melting and boiling points
•Low because only a small amount of heat is needed to overcome the weak forces of attraction between molecules.
Electrical conductivity
•Cannot conduct electricity in both molten and liquid and are not electrolyte.
•Covalent compounds are neutral molecules.
Water solubility
•Most are insoluble in water but soluble in organic solvent.
Volatility
•Highly volatility because of the weak “Van der Waals” force.