Atoms form chemical bonds to achieve stable electron configurations. They follow the octet rule by gaining, losing, or sharing electrons to acquire eight electrons in their valence shell. There are four main types of chemical bonds: ionic bonds form when electrons are completely transferred between atoms, covalent bonds form when electrons are shared between atoms, and polar and nonpolar covalent bonds differ based on whether the electron sharing is equal or unequal. Chemical bonds determine many properties of compounds including their physical state, solubility, and ability to conduct heat and electricity.

1. CHEMISTRY
TOPIC : STRUCTURE OF MOLECULES.

2. WHAT IS CHEMICAL BOND?
 Chemical bond is defined as a
force of attraction between
atoms that holds them together
in a substance.
 Why do atoms form chemical
bond?
 Atoms achieve stability by
attaining nearest noble gas
configuration i.e. ns2, np6 .
 2 or 8 electrons in the valence
shell of an atom is sign of
stability for atoms.

3. WHAT IS OCTET AND DUPLET RULE ?
 Octet rule
 Attaining of 8 electrons in the valence shell of an
atom is called octet rule.
 Duplet rule
 Attaining of two electrons in the valence shell of an
atom is called duplet rule.
 Elements like hydrogen and helium follow duplet
rule.

4. HOW DO ATOMS FOLLOW OCTET RULE?
 An atom can accommodate 8 electrons in its
valence shell in three ways.
 By giving valence shell electrons (if they are less
than three) to other atom.
 By gaining valence shell electron (if the valence
shell has 5 or more than 5 electrons)
 By sharing valence shell electrons.

5. TYPES OF CHEMICAL BOND
 Chemical bonds are of four types:
 Ionic bond
 Covalent bond
 Dative or coordinate covalent bond
 Metallic bond

6. BONDING AND NON BONDING ELECTRONS
 Bonding electrons:
 The valence electrons which are involve in
chemical bonding are termed as bonding electrons.
 Non bonding electron:
 The electrons that belongs to valence shell of an
atom but do not involve in boding is called non
bonding electrons.
 7N= 1s2, 2s2,2p3

7. IONIC BOND
 The type of chemical bond,
which is formed due to
complete transfer of electron
from one atom to another atom
is called ionic bond
 The elements of group 1 and 2
have tendency to lose electron
while group 15 to 17 have
tendency to gain electron.

8. EXAMPLE OF IONIC BOND
 11Na=1s2,2s2,2p6, 3s1
 17Cl=1s2,2s2,2p6, 3s2,3p5
 𝑁𝑎 → 𝑁𝑎+ + 1e- (1s2,2s2,2p6=Ne)
 𝐶𝑙 + 1𝑒
−
→ 𝐶𝑙
−
(1s2,2s2,2p6,3s2,3p6=Ar)
 Na+ + Cl- → NaCl

9. PROPERTIES OF IONIC COMPOUNDS
 Ionic compounds are solid in nature because they
are made up of positive and negative charges .
Theses charges held together with strong
electrostatic force of attraction.
 They have high melting and boiling point
 They are good conductor of heat and electricity in
molten or solution form
 They are mostly crystalline solid
 They are easily soluble in water.

10. COVALENT BOND
 The type of bond, which is
formed due to mutual sharing
of electrons is called covalent
bond.
 Covalent bond form between
atoms of group 13 to group 17.

11. FORMATION OF COVALENT BOND

12. TYPES OF COVALENT BOND
 Depending upon number of bond pair covalent
bond divided in to three types.
 Single covalent bond
 Double covalent bond
 Triple covalent bond

13. SINGLE COVALENT BOND
 When one electron is contributed by each bonded atom
is called single covalent bond.
 Single covalent bond is indicated by a line (-) between
bonded atoms.
 For example HCl, Cl2, CH4

14. DOUBLE COVALENT BOND
 When each bonded atom contributes two electrons, two
bond pair are shared and a double covalent bonds
formed
 The bond pairs are indicated as double line (=) between
atoms
 For example O2, C2H4

15. TRIPLE COVALENT BOND
 When each bonded atom contributes three electrons, three
bond pair are shared and a triple covalent bond formed.
 The bond pairs are indicated as three line (≡) between
atoms.
 For example N2 and C2H2.

16. PROPERTIES OF COVALENT COMPOUNDS
 They have usually low melting and boiling point. But
large molecules with three dimensional pattern are
stable and hard so they have high melting and
boiling point.
 They are bad conductors of heat and electricity but
compounds having polar character show
conductance when dissolve in polar solvent.
 They are insoluble in water but soluble in non
aqueous solution like benzene, ether etc.

17. POLAR COVALENT BOND
 Covalent bond is form
between different type of
atoms ( Hetero-atoms)
 The bond pair of electron
will not be attracted equally.
 There is a difference of
electronegativity between
two covalently bonded
atoms.
 For example HCl, H2O,HF

18. NON POLAR COVALENT BOND
 Covalent bond is form
between same type of
atoms ( Homo-atoms)
 The bond pair of
electron will be
attracted equally.
 For example:
 H2 and Cl2

19. DIFFERENTIATE BETWEEN POLAR AND NON
POLAR COMPOUNDS
 Polar compounds
dissolve in water.
 They are good
conductor of heat and
electricity when
dissolve in polar
compounds
 Non polar compounds
do not dissolve in
water.
 They are bad
conductors of heat and
electricity
Polar compounds Non polar compounds