(40) GCSE Chemistry Revision "The Nuclear Model"

Nuclear Model of Atomic Structure

• Introduction to Atomic StructureBy the end of this video, students should be able to:

  • Describe the nuclear model of atomic structure.

  • Explain modifications made to the nuclear model, including electron energy levels, protons, and neutrons.

• Transition from Plum Pudding Model

  • The early model of atomic structure was called the Plum Pudding model.

  • It was replaced due to results from the alpha scattering experiment.

  • Nuclear Model: Most of an atom is empty space with a positive nucleus at its center, which contains greatly most of the atom's mass, surrounded by negative electrons.

Modifications to the Nuclear Model

• Electron Energy Levels

  • Proposed by Niels Bohr: Electrons orbit the nucleus at specific distances (not just in random areas).

  • These designated paths are known as energy levels or shells.

  • Bohr's proposal was accepted due to alignment with experimental results from other scientists.

• Discovery of Protons

  • The positive charge in the nucleus is due to protons.

  • Example:

    • Hydrogen: 1 proton in the nucleus.

    • Helium: 2 protons in the nucleus.

  • The number of protons defines the amount of positive charge within the nucleus.

• Discovery of Neutrons

  • James Chadwick discovered that the nucleus also contains neutral particles known as neutrons.

  • This represents the modern view of the nucleus, consisting of both protons and neutrons.

Dimensions of Atomic Structure

• Size Measurements

  • Radius of an Atom: Approximately 0.1 nanometers (1 × 10^-10 m).

  • Radius of the Nucleus: Approximately 1 × 10^-14 m (less than 1/10,000 the radius of the atom).

  • Nearly all mass of the atom is concentrated in the nucleus.

Relative Charges and Masses of Subatomic Particles

• Relative Charges

  • Protons: Relative charge of +1.

  • Neutrons: Relative charge of 0 (neutral).

  • Electrons: Relative charge of -1.

• Overall Charge of Atoms

  • Atoms have no overall charge because the number of electrons equals the number of protons; their charges cancel each other out.

• Relative Masses

  • Protons and Neutrons: Relative mass of 1 (equivalent mass).

  • Electrons: Much smaller relative mass compared to protons and neutrons (exact value is not necessary to know).

  • Exam preparation involves understanding these concepts as they frequently appear in questions.