2017-11-30
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TYPES OF BOND
Atoms bond to each other in one of four ways:
i) ionic bonding
An ionic bond is an attraction between oppositely charged ions, which are formed by the transfer of electrons from one atom to another.
Eg In sodium chloride, each sodium atom transfers an electron to a chlorine atom. The result is a sodium ion and a chloride anion. These two ions attract each other to form a stable compound.
ii) Covalent bonding
A covalent bond is a pair of electrons shared between two atoms.
In a normal covalent bond, each atom provides one of the electrons in the bond. A covalent bond is represented by a short straight line between the two atoms.
Eg water
In a dative covalent bond, one atom provides both electrons to the bond.
A dative covalent bond is a pair of electrons shared between two atoms, one of which provides both electrons to the bond.
A dative covalent bond is represented by a short arrow from the electron providing both electrons to the electron providing neither.
Eg ammonium ion
Covalent bonding happens because the electrons are more stable when attracted to two nuclei than when attracted to only one.
Covalent bonds should not be regarded as shared electron pairs in a fixed position; the electrons are in a state of constant motion and are best regarded more as charge clouds.
iii) Metallic bonding
A metallic bond is an attraction between cations and a sea of electrons.
Metallic bonds are formed when atoms lose electrons and the resulting electrons are attracted to all the resulting cations.
Eg Magnesium atoms lose two electrons each, and the resulting electrons are attracted to all the cations.
Metallic bonding happens because the electrons are attracted to more than one nucleus and hence more stable. The electrons are said to be delocalized – they are not attached to any particular atom but are free to move between the atoms.
