9th Class chemistry notes of unit 4

Atoms of different elements react to attain noble gas configuration, which is stable one.

Chemical bonds may be formed by complete transfer of electrons (ionic); mutual sharing (covalent) or by donation from an atom(coordinate or dative covalent).

Metals have the tendency to lose electrons easily forming cations.

Non-metals have tendency to gain electrons and form anions.

In ionic bonding strong electrostatic force hold ions together.

Ionic compounds are solids with high melting and boiling points.

Covalent bonds among non-metals are weaker than ionic bonds.

Ionic bonds are non-directional, but covalent bonds are formed in a particular direction.

Covalent bonds formed between similar atoms are non-polar while between different atoms are polar.

In covalent bonding single, double or triple covalent bond is formed by sharing of one, two or three electron pairs by the bonded atoms.

Coordinate covalent bond is formed between electron pair donors and electron pair acceptors.

Metallic bond is formed between metal atoms due to free electrons.

In addition to chemical bonds, intermolecular forces of attraction exist between polar molecules.

Hydrogen bonding exists between the hydrogen atom of one molecule and highly electronegative atom of other molecule.

Hydrogen bonds affect the physical properties of the compounds.

Properties of the compounds depend upon the nature of bonding present in the compound.

Ionic compounds are crystalline solid with high melting and boiling points.

Covalent compounds exist in molecular form in three physical states.

Polar and non- polar covalent compounds have different properties.

Metals have shining surface. They are good conductor of electricity and are malleable and ductile.

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