L3 Bonding

• Chemical bonding refers to the formation of a chemical bond between two or more atoms, molecules or ions to give rise to a chemical compound.
• The force of attraction between positively and negatively charged particles or ions is called and electrostatic force.
• The bond that forms between positive and negative ions is called an ionic bond.
• There is a transfer of electrons during the formation of an ionic bond.
• Ionic bonds form between a metal and a non-metal.
• Ionic bonding is observed because metals have few electrons in their outer-most orbitals.
• By losing the few valence electrons, the metals can achieve noble gas configuration and satisfy the octet rule.
• Non-metals that have close to eight electrons in their outer shells tend to readily accept electrons to achieve noble gas configuration.
• In ionic bonding, more than one electron can be donated or received to satisfy the octet rule.
• The charges on the anion and cation correspond to the number of electrons donated or received.
• Property of Ionic Compounds:

  • They are usually crystalline solids. Because of this crystalline structure, the ions are held rigidly in place. This prevents crystals from bending and instead makes ionic crystals very brittle.
• Property of Ionic Compounds:

  • They have high melting points and high boiling points. For example, salt does not melt on a common household stovetop because sodium chloride would need to reach 801°C to melt. The high melting points are the results of very strong ionic bonds in the compounds.
• Property of Ionic Compounds:

  • They are usually soluble in water but insoluble in organic solvents because the water molecule, being polar in nature, breaks the ionic bond and interact strongly with positive-negative ions of the ionic compound.
• Property of Ionic Compounds:

  • They conduct electricity when dissolved in water or when melted, because their ions are free to move from place to place. Ionic compounds cannot conduct electricity when solid, as their ions are held in fixed positions and cannot move.
• Property of Ionic Compounds:

  • The formula for ionic compounds is always an empirical formula because it shows the smallest, whole-number ratios between the cations and anions. The actual number of ions in a sample of an ionic compound will be vary large and will vary from sample to sample.
• A covalent bond consists of the mutual sharing of one or more pairs of electrons between two atoms.
• Types of Covalent Bonds:

  1. Single Bonds e.g. water
  2. Double Bonds e.g. carbon dioxide
  3. Triple Bonds e.g. nitrogen
• Property of Covalent Substances:

  • Covalent bonding exists in solids, liquids, and gases at room temperature. The covalent compounds are formed by the sharing of electrons between the bonded atoms. The covalent bonds are held together by the weak Vander Waal force due to which they have low melting and boiling points.
• Property of Covalent Substances:

  • Do not conduct electricity as they are made up of neutral particles because the resultant mobile particles are neutral molecules. Their movement cannot be used to carry an electric charge.
• Property of Covalent Substances:

  • The melting and boiling points are lower than those of ionic solids. Melting of water compounds involves breaking ionic bonds whereas the melting of covalent compounds involves disrupting the weak forces between molecules.
• Property of Covalent Substances:

  • Lower solubility in water than ionic solids. This is because water dissolves polar substances, which is the consistency of the ionic compound, whereas covalent compounds are non-polar.