Chemical Bonding part 2

(f) Hydrogen bonding – a specialized form of permanent dipole –dipole interaction.
Hydrogen bonding is formed between the hydrogen atom of an ammonia or water molecule (with a small positive charge) in one molecule and the lone pair of electrons of the electronegative atom such as nitrogen, oxygen or fluorine in another neighbouring molecule.

(g) Bond length – the distance between the nuclei of the two atoms in the covalent bond or sum of covalent (atomic) radii.
The shorter the bond length, the stronger the covalent bond.

Bond energy – the amount of energy required to break one mole of covalent bond at gaseous state.
The greater the bond energy, the stronger the bond.

Bond polarity – the dipole-dipole intermolecular forces between the slightly positively-charged ends of one molecule to the negative end of another or the same molecule.

(h) Van der waals’ forces – the induced dipoles are due to the random movement of electrons around the atoms. At any point of time, the electron distribution may be slightly displaced towards one side of an atom or molecule, making that side slightly negative, and the opposite side slightly positive.

Permanent dipole-dipole attraction – it is the attraction between molecules that have permanent dipole moments (polar molecules) in liquid and solid states.

(j) Ionic bonding – they are formed when electrons are transferred from the valence shell of atoms of one element to other atoms.
1. high melting and boiling point
2. soluble in water, insoluble in organic solvents (exceptions)
3. poor electrical conductors in solid state but good conductors in molten and aqueous state.
4. hard and brittle

Covalent bonding – the sharing (pairing) of electrons between atoms.

Hydrogen bonding – a specialized form of permanent dipole –dipole interaction.

Metallic bonding – the force of attraction between positive metal ions and the negative delocalized electrons.
1. high degree of electrical conductivity
2. high degree of thermal conductivity
3. high melting and boiling point
4. shiny metal lustre
5. insoluble in water
6. malleable

Van der waals’ forces – the induced dipoles are due to the random movement of electrons around the atoms. At any point of time, the electron distribution may be slightly displaced towards one side of an atom or molecule, making that side slightly negative, and the opposite side slightly positive.