tYPES of bondstYPES of bonds

1.1. Ionic bondIonic bond :Formed by transfer of Formed by transfer of electronselectrons

2.2. Covalent bond:Covalent bond: Formed by ormed by sharing electronssharing electrons

3.3. Metallic bond:Metallic bond: Delocalization of Delocalization of electrons over large area of covalent electrons over large area of covalent bondbond

IONic Bonding

• Electrons are transferred between valence shells of atoms

• Ionic compounds are made of ions

• Ionic compounds are called Salts or Crystals

NOT MOLECULES

Covalent BondingCovalent Bonding

Covalent compounds form by sharing electrons to attain a noble gas electron configuration

Regardless of the type of bond, the Octet Rule still must be obeyed (8 valence electrons)

Types of covalent bonds

• Non Polar covalent bond:

This type of bond is This type of bond is formed when electrons are formed when electrons are shared equally…shared equally…

• Polar covalent bond:

This type of bond is This type of bond is formed due to un equal formed due to un equal sharing of electronssharing of electrons..

.

Oxygen AtomOxygen Atom Oxygen AtomOxygen Atom

Oxygen Molecule (OOxygen Molecule (O22))

Non polar covalent bond – Equal sharing of electrons

Other cases of Other cases of covalent bondcovalent bond

• DOUBLE bond – atoms that share two e- pairs

(4 e-)

O O• TRIPLE bond

– atoms that share three e- pairs (6 e-)

N N

Methane CHMethane CH44

• This is the finished Lewis dot This is the finished Lewis dot structure structure

How did we get here?How did we get here?

Steps or formation of Steps or formation of Covalent bondCovalent bond

• Step 1– count total valence e- involved

• Step 2– connect the central atom (usually the first

in the formula) to the others with single bonds

• Step 3– complete valence shells of outer atoms

• Step 4– add any extra e- to central atom

IF the central atom has 8 valence e- surrounding it . . YOU’RE DONE!

Sometimes . . .

• You only have two atoms, so there is no central atom, but follow the same rules.

• Check & Share to make sure all the atoms are “happy”.

Cl2 Br2 H2 O2 N2 HCl

Properties of Molecular Substances

Physical propertiesPhysical properties Covalent compoundsCovalent compounds

States (at room temperature)States (at room temperature) Liquid & gasLiquid & gas

Electrical conductivityElectrical conductivity Usually noneUsually none

Boiling point and Melting pointBoiling point and Melting point Varies, but usually lower than Varies, but usually lower than ionic compoundsionic compounds

Solubility in waterSolubility in water Varies, but usually lower than Varies, but usually lower than ionic compoundsionic compounds

Thermal conductivityThermal conductivity Usually lowUsually low

Covalent bonding

Done byP.Dhanush,Tenth class.Narayana e.techno