Formation of Sodium Chloride

Formation of Sodium Chloride

• Ionic bonding occurs when a metallic element loses electrons to a non-metallic element, creating ions.
• Sodium (Na) has an electron configuration of 2, 8, 1 and can lose one electron to form Na+ (2, 8).
• Chlorine (Cl) has a configuration of 2, 8, 7 and can gain one electron to form Cl- (2, 8, 8).
• The oppositely charged ions (Na+ and Cl-) attract each other, forming sodium chloride (NaCl).

Properties of Metallic Bonds

• Strong metallic bonds, such as in iron, make metals difficult to break; weaker bonds, like in sodium, allow cutting with a knife.
• Metals are effective conductors of heat and electricity due to mobile electrons that can move freely.
• Many metals exhibit malleability and ductility, being able to withstand stress without breaking.

Hydrogen Bonds

• Hydrogen bonds form when hydrogen is covalently bonded to electronegative elements (N, O, F).
• These bonds arise from the dipole created by the unequal sharing of electrons, causing electrostatic attraction.
• Hydrogen bonds elevate the melting and boiling points of compounds containing them.

Air Composition and Reactions

• Air comprises nitrogen (78%), oxygen, and trace impurities.
• Chemical reactions in air can release various products upon heating, such as:
  • 2Mg + O2 → 2MgO (magnesium oxide)
  • C + O2 → CO2 (carbon dioxide from complete combustion)
  • 2C + O2 → 2CO (carbon monoxide from incomplete combustion).

Properties of Ionic Compounds

• Ionic compounds consist of aggregates of charged ions rather than discrete molecules.
• They dissolve well in polar solvents (e.g., water) but not in non-polar solvents (e.g., benzene).
• Ionic compounds are solid at room temperature, have high melting/boiling points, and conduct electricity when molten or dissolved in water.

Covalent Bonds

• Covalent bonds involve the sharing of electron pairs between atoms, leading to stable molecules such as Cl2.
• Each chlorine atom shares one electron, resulting in each atom achieving a complete outer shell.
• Property: Covalent compounds typically exist as gases or liquids with low melting and boiling points.

Properties of Covalent Compounds

• Many covalent compounds are gases or liquids at room temperature due to weak intermolecular forces.
• They are generally soluble in organic solvents and do not conduct electricity due to the absence of ions.
• Co-ordinate (or dative) bonds involve one atom providing both electrons for the shared pair, as seen in compounds like ammonia (NH3).

Characteristics of Metallic Bonds

• Metallic bonds involve free-moving valence electrons in a crystal lattice, allowing for high electrical and thermal conductivity.
• Metals typically possess high melting and boiling points due to the strong attractions between metal ions and the electron cloud.

Co-ordinate Covalent Bonds

• In co-ordinate covalent bonds, one atom donates both electrons for the bond, forming a lone pair.
• Examples include the interaction between ammonia and hydrochloric acid, producing a co-ordinate covalent bond with the nitrogen atom.
• The properties of co-ordinate covalent compounds closely resemble those of standard covalent compounds.