Study Guide for SCH 3202 Chemistry of S and P Block Elements

SCH 3202 Chemistry of S and P Block Elements

Instructor Information

  • Lecturer: Dr. Bosire Geoffrey
  • Affiliation: Senior Lecturer, Department of Chemistry, University of Nairobi

Course Assessment Breakdown

  • Continuous Assessment Tests: 30%
  • Examination: 70%
  • Total: 100%

Course Outline

  1. The s- and p-blocks in the Periodic Table
  2. Periodicity of properties of the s and p-block elements
  3. Elements in groups I to VIII (1, 2, 13-18)
  4. Some applications of the elements in groups I to VIII
Overview of S and P Block Elements
  • The periodic table is divided into s, p, d, and f blocks based on the type of orbital in which the atom's outermost electrons reside.
    • Example of s-block:
      • Lithium (Li): Electron configuration [He]2s1, thus belongs to the s-block.
    • Example of p-block:
      • Boron (B): Electron configuration [He]2s2 2p1, thus belongs to the p-block.
    • Example of d-block:
      • Molybdenum: Electron configuration [Kr]5s1 4d5, thus belongs to the d-block.
  • D- and f-block elements are covered in other courses; this course focuses on the main group elements (s and p-block).

IUPAC Naming Conventions

  • The periodic table has 18 groups, but the focus is on main group elements 1-8.
  • In p-block elements from periods 4 to 7, typically only valence electrons are shown while core electrons are omitted.
  • Example of Electron Configuration and Valence Electrons:
    • Gallium (Ga): Complete configuration [Ar]3d10 4s2 4p1 (focus only on 4s2 4p1 for valence).
Key Chemicals Involving s and p-block Elements
  1. Sodium carbonate (Na2CO3): Vital for glass manufacturing.
  2. Sodium chloride (NaCl)
  3. Sulfuric acid (H2SO4)
  4. Phosphate rock (MPO4)
  5. Nitrogen (N2)
  6. Ethylene (C2H4)
  7. Oxygen (O2)
  8. Lime (CaO)
  9. Propylene (C3H6)
  10. Ammonia (NH3)
  11. Chlorine (Cl2)
  12. Phosphoric acid (H3PO4)
  13. Sodium hydroxide (NaOH)
  14. Dichloroethane (C2H4Cl2)
  15. Sulfur (S8)
  16. Nitric acid (HNO3)
  17. Ammonium nitrate (NH4NO3)
  18. Benzene (C6H6)
  19. Urea ((NH2)2CO)
  20. Ethylbenzene (C6H5C2H5)
  21. Gypsum (CaSO4·2H2O), important in cement manufacturing.
    • Example: Crystals found in Naica mine, Mexico.

Properties of s- and p-block Elements

General Characteristics of Elements
  • Elements in groups I to VIII have similar electronic configurations; they exhibit many similar chemical and physical characteristics.
  • S-block (Group I and II) Trends:
    • Element sizes increase down the group.
    • Elements of group I are soft metals with low melting points.
    • Low ionization energies are a key characteristic.
Atomic and Ionic Size
  • The atomic radius of elements becomes larger down the group due to increased principal quantum energy levels.
  • Covalent Radius:
    • For diatomic molecules, it is defined as half the distance between two nuclei of the bonding atoms.
  • Example of Atomic Radius Trends:
    • Atomic radius decreases from Li to Ne across a period but increases down a group (e.g. Na is larger than Li).
    • Discontinuity occurs at Ga in group 3 due to d-block contraction.
Ionization Energy
  • Defined as the energy required to remove the most loosely bound electron from a gaseous atom or ion.
  • Various factors affecting ionization energy include size of the atom, charge of the nucleus, and shell effect of inner electrons.
  • Ionization energies typically increase across a period and decrease down a group.
Electron Affinity
  • Electron affinity refers to the energy change when an electron is added to a neutral atom in the gas phase.
    • Examples of Electron Affinity Values:
    • H: -73 kJ/mol
    • Cl: -349 kJ/mol
    • O: -141 kJ/mol
Electronegativity
  • Defined as the tendency of an atom to attract electrons in a bond.
  • The Pauling scale is commonly used to quantify electronegativities. For example, covers the following:
    • Fluorine (F) has the highest electronegativity (4.0), thus attracts electrons strongly.

Group-Specific Notes

Group I: Alkali Metals
  • Occurrence and Extraction:
    • Sodium is extracted from rock salt (NaCl) via electrolysis of molten salts.
  • Key Properties:
    • Low densities and melting points, soft metals.
    • High reactivity with nonmetals, forming ionic compounds (often with halogens).
  • Applications: Used in soap making, glass production, etc.
Group II: Alkaline Earth Metals
  • Occurrence & Extraction:
    • Occur as naturally occurring compounds (e.g., Mg from dolomite).
  • Applications: Used in various industrial processes and as reducing agents.
Group III: Boron Group
  • Key Characteristics:
    • B is non-metallic; the rest (Al, Ga, In, Tl) are considered metallic; exhibit variable oxidation states.
  • Reactivity: Al reacts with oxygen and can form complex ions.
Group IV: Carbon Group
  • Properties:
    • Carbon can exhibit allotropy (diamond and graphite differ vastly in properties).
Group V: Nitrogen Group
  • Reactivity:
    • Stable gas (N2) and other solid elements (P, As, Sb, Bi).
Group VI: Chalcogens
  • Oxygen (O2) as a critical element for life, used in combustion processes.
Group VII: Halogens
  • Reactivity: Strong oxidizers, element properties decrease down the group (F > Cl > Br > I).
Group VIII: Noble Gases
  • Extremely low reactivity due to their complete valence shell.

Conclusion

  • Understanding s- and p-block elements help gauge their behaviors and applications across multiple domains in chemistry, industry, and beyond.

References

  • G.L Miessler and D.A Tarr, Inorganic Chemistry
  • N.N Greenwood and A. Earnshaw, Chemistry of the Elements
  • R.B. Heslop and P.L. Robinson, Inorganic Chemistry, A Guide to Advanced Study.
  • Additional references for deeper understanding included in the syllabus.