Answers_V2_IGCSE_BK_2_ATOMIC

ACG Parnell College IGCSE Chemistry: Atomic Structure Notes

Chapter 2: Atomic Structure 2023-2025

Objectives

• Atomic Structure and the Periodic Table

  • Describe the atom's structure (nucleus with neutrons and protons, electrons in shells).

  • State relative charges and masses of subatomic particles:

    • Proton: +1 charge, mass = 1

    • Neutron: 0 charge, mass = 1

    • Electron: -1 charge, negligible mass

  • Definitions:

    • Proton Number / Atomic Number (Z): Number of protons in nucleus.

    • Mass Number / Nucleon Number (A): Sum of protons and neutrons.

  • Determine electronic configurations for elements/ions (proton numbers 1-20).

  • Characteristics of Group VIII Noble Gases: full outer shell.

  • Relationship between group number, outer shell electrons, and metallic/non-metallic character.

  • Trends across periods and groups.

Isotopes

• Definition: Isotopes are atoms of the same element with different numbers of neutrons.

• Examples:

  • Carbon-12: 6 protons, 6 neutrons.

  • Carbon-13: 6 protons, 7 neutrons.

  • Carbon-14: 6 protons, 8 neutrons.

• Same chemical properties due to identical electron configurations.

• Calculation of relative atomic mass from isotopic abundances.

Arrangement of Elements in the Periodic Table

• The Periodic Table: organized by increasing atomic number (Z).

• Trends:

  • Change from metallic to non-metallic character across a period.

  • Group number indicates the charge of ions formed (e.g. Group I forms +1 ions).

  • Elements in the same group exhibit similar chemical properties due to similar electronic configurations.

  • Example Groups:

    • Group I: Alkali Metals (1 valence electron)

    • Group II: Alkaline Earth Metals (2 valence electrons)

    • Group VII: Halogens (7 valence electrons)

    • Group VIII: Noble Gases (8 valence electrons, stable)

• Periods:

  • Atoms in the same period have the same number of occupied electron shells.

Electronic Configuration

• Definition: arrangement of electrons in shells around the nucleus.

• Shell configurations:

  • 1st shell: max 2 electrons

  • 2nd shell: max 8 electrons

  • 3rd shell: max 8 electrons for stable configuration.

Important Points

• Elements in the same group have:

  • Same number of valence electrons.

  • Similar properties due to electron arrangement.

• Ions: Formed when atoms lose or gain electrons to achieve a noble gas configuration.

  • Example: Sodium (Na) loses one electron to form Na+ (2, 8).

  • Example: Oxygen (O) gains two electrons to form O2- (2, 8).

Isotope Calculations

• Example: Calculate relative atomic mass from isotopes.

  • Bromine-79 (50.7%), Bromine-81 (49.3%).

• Exercises:

  • Define isotopes and provide examples.

  • Calculate relative atomic mass based on isotope percentages.

The Periodic Table

• Vertical columns: Groups (similar properties due to valence electrons).

• Horizontal rows: Periods (similar number of shells).

• Properties:

  • Metals: Shiny, malleable, good conductors.

  • Non-metals: Dull, brittle, poor conductors.

  • Metalloids: Hybrid properties.

Questions and Exercises

• Multiple Choice & Structured Questions:

  • e.g., determine the number of protons and electrons in ions; compare isotopes; discover electron configurations.

  • Example of questions focusing on isotopes and atomic structures, summarizing major points from previous topics.

Conclusion

• Understanding atomic structure, isotopes, and their implications play a crucial role in comprehending chemistry and the Periodic Table's structure.