Chemical Bonding and Reactions
Covalent Compound
Covalent bonds are the bonds which are formed due to
the equal sharing of electrons between two atoms. These chemistry notes are provided by
Chemistry Notes Info Organization www.ChemistryNotesInfo.com , This type of bonds
(i.e. covalent bonds) is formed in atoms which carry four or more than four
electrons in outermost shell, generally sharing of electrons happen in two ways
–
1.
Equal Sharing – Covalent Bond
2.
One Side Sharing – Coordinate Bond
Covalent Compounds
Compound
which are formed as a result of covalent bonding and containing covalent bonds
are known as Covalent Compounds.
Example:
Hydrogen, Chlorine, Oxygen, Water, Ethanol etc.
Types of Covalent Bonds
Covalent
Bonds are of three types which are as follows-
1. Single
Covalent Bonds
2. Double
Covalent Bonds
3. Triple
Covalent Bonds
Single Covalent Bonds
Bonds
which are formed due to sharing of single pair of electrons between two atoms
are called single covalent bond. It is represented by single line (-)
Example:
Formation of H2 molecule, Formation of Cl2 molecule.
i. Formation of Hydrogen (H2) molecule:
In the outermost shell of hydrogen atom, it have single electron, which
it share with another hydrogen atom to acquire inert configuration of helium so
single bond is formed between these two hydrogen atoms and this single covalent
bond is represented by single line (-)
ii. Formation of Chlorine Molecule (Cl2) :
In
the outermost shell of chlorine atom, it have seven electrons, it share its one
valence electron with another chlorine atom to form chlorine molecule by single
covalent bond.
Double Covalent Bonds
Bonds
which are formed due to sharing of double pair of electrons between two atoms
are called double covalent bond. It is represented by double line (=)
Example:
Formation of O2 molecule.
i. Formation of Oxygen (O2) molecule:
In the outermost shell of oxygen atom, it
have six electrons, it share its two valence electrons with another oxygen atom
to form oxygen molecule by double covalent bond.
Triple Covalent Bonds
Bonds
which are formed due to sharing of triple pair of electrons between two atoms
are called triple covalent bond. It is represented by triple lines
Example:
Formation of N2 molecule.
i. Formation of Nitrogen (N2) molecule:
In the outermost shell of nitrogen atom, it
have five electrons, it share its three valence electrons with another nitrogen
atom to form nitrogen molecule by triple covalent bond.
Characteristics of covalent compounds
1. Crystal Structure:
Crystal structure of covalent compounds is
formed from atoms or molecules. Crystal of covalent compounds are divided in
three parts as –
i.
These are crystals of covalent compounds
whose molecule are very small and these molecules are held together by vander
waals forces.
Example:
Sulphur, Iodine.
ii.
These are crystals of covalent compounds
whose molecule are very large due to combination of every atom with other atom
by covalent bonds.
Example: Diamond, Silica.
iii.
These are crystals of covalent compounds
whose have separate layers.
Example: Graphite.
2. Physical Nature:
Due to weaker force of attraction
between the molecules of the covalent compounds, maximum covalent compounds are
gases or liquids but some covalent compounds exist as solid like Urea, Sugar,
Glucose, and Naphthalene.
3. Solubility:
Covalent compounds are not soluble in polar solvents like water but are soluble in non-polar solvent like alcohol, ether, carbon tetra chloride.4. Melting Point and Boiling Point ( MP and BP) :
Melting and boiling
points of covalent compounds are very low because very less energy is required
to overcome the weak force of attraction between the neutral molecules in the
covalent compound. But Diamond and Graphite are exception because they have
very high melting and boiling points.
5. Conductivity:
Covalent compounds do
not have ions so they do not conduct electricity but some polar covalent
compounds conduct very less electricity.
9th Class Chemical Bonding and Reactions Part 1
9th Class Chemical Bonding and Reactions Part 3
Polar Covalent Bond
In the
covalent compound if one is the more is more electronegative than other atom,
then shared pair of electrons is attracted towards more electronegative atom so
it acquire or obtain some partial negative charge which is represented by delta
negative (d-)
and other atom acquire some partial positive charge which is represented by
delta positive (d+) therefore polar bond is form, which
is known as Polar covalent bond.
Example : Hydrogen Chloride Molecule.
In HCl molecule, Chlorine is more
electronegative than Hydrogen so chlorine acquires partial negative charge and
hydrogen acquire partial positive charge.
Characteristics of Polar Covalent Compounds
i.
Polar
covalent compounds are approximately 80% covalent and 20% ionic so they so characteristics
of both covalent and ionic (or electrovalent) compounds.
ii.
In
solution forms, polar covalent compounds are good conductor of electricity.
Example: HCl
iii.
As
compared to pure non-polar covalent compounds and electrovalent compounds, the
melting point and boiling point of polar covalent compound are higher.
9th Class Chemical Bonding and Reactions Part 1
9th Class Chemical Bonding and Reactions Part 3
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