Atomic Structure and Chemical Bonding Fundamentals

Posted on Jan 26, 2025 in Chemistry

Ionization Enthalpy

The amount of energy required to remove electrons one by one is known as the enthalpy of ionization. The energy required to remove the last electron is called the first ionization enthalpy, and to remove the second last electron is called the second ionization energy, and so forth.

Electron Configuration

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6

Mass and Atomic Numbers

Mass number = Number of protons + Number of neutrons

Atomic Number = Number of protons + Number of electrons

Periodic Table: First 30 Elements

  1. H – Hydrogen
  2. He – Helium
  3. Li – Lithium
  4. Be – Beryllium
  5. B – Boron
  6. C – Carbon
  7. N – Nitrogen
  8. O – Oxygen
  9. F – Fluorine
  10. Ne – Neon
  11. Na – Sodium
  12. Mg – Magnesium
  13. Al – Aluminum, Aluminium
  14. Si – Silicon
  15. P – Phosphorus
  16. S – Sulfur
  17. Cl – Chlorine
  18. Ar – Argon
  19. K – Potassium
  20. Ca – Calcium
  21. Sc – Scandium
  22. Ti – Titanium
  23. V – Vanadium
  24. Cr – Chromium
  25. Mn – Manganese
  26. Fe – Iron
  27. Co – Cobalt
  28. Ni – Nickel
  29. Cu – Copper
  30. Zn – Zinc

Hybridization in Chemical Bonding

Hybridization was introduced to explain molecular structure when the valence bond theory failed to correctly predict them. It is experimentally observed that bond angles in organic compounds are close to 109o, 120o, or 180o. According to Valence Shell Electron Pair Repulsion (VSEPR) theory, electron pairs repel each other, and the bonds and lone pairs around a central atom are generally separated by the largest possible angles.

sp3 Hybridization

sp3 hybridization can explain the tetrahedral structure of molecules. In it, the 2s orbitals and all three of the 2p orbitals hybridize to form four sp orbitals, each consisting of 75% p character and 25% s character. The frontal lobes align themselves in a manner that minimizes electron repulsion in this structure.

sp2 Hybridization

sp2 hybridization can explain the trigonal planar structure of molecules. In it, the 2s orbitals and two of the 2p orbitals hybridize to form three sp orbitals, each consisting of 67% p and 33% s character. The frontal lobes align themselves in the trigonal planar structure, pointing to the corners of a triangle to minimize electron repulsion and improve overlap. The remaining p orbital remains unchanged and is perpendicular to the plane of the three sp2 orbitals.

sp Hybridization

sp Hybridization can explain the linear structure in molecules. In it, the 2s orbital and one of the 2p orbitals hybridize to form two sp orbitals, each consisting of 50% s and 50% p character. The front lobes face away from each other and form a straight line, leaving a 180° angle between the two orbitals. This formation minimizes electron repulsion. Because only one p orbital was used, we are left with two unaltered 2p orbitals that the atom can use. These p orbitals are at right angles to one another and to the line formed by the two sp orbitals.

Hydrogen Bonds

Hydrogen bonds can be classified into two types:

a) Intermolecular hydrogen bond: This type of bond is formed between two different molecules of the same or different substances.

b) Intramolecular hydrogen bond: This type of bond is formed between the hydrogen atom and a highly electronegative atom (F, O, or N) present in the same molecule.