Rutherford gold

Rutherford's Gold Foil Experiment

  • Proposed nuclear theory of the atom with three key parts:

    1. Most mass and all positive charge are in the nucleus.

    2. Atom's volume is mostly empty space with electrons dispersed.

    3. Number of electrons equals number of protons, making the atom electrically neutral.

Structure of the Atom

  • J.J. Thomson's model: atom as a sphere of positive charge with embedded negative particles.

  • Rutherford's Gold Foil Experiment:

    • Directed alpha particles at gold foil. ( alpha particles are positively charged)

    • Most alpha particles passed through; few bounced back, indicating a small, dense nucleus. This led to the conclusion that the majority of the atom is empty space, with the nucleus containing most of the atom's mass and positive charge.

    • The nucleus is positvely charged with protons and neutrons. The electrons are on the outer shell surrounding the nucleus.

Subatomic Particles

  • Protons: positive charge (+1.60218 × 10⁻¹⁹ C).

  • Electrons: negative charge (-1.60218 × 10⁻¹⁹ C), equal in magnitude to protons.

  • Neutrons: neutral charge, found in the nucleus.

Atomic and Mass Numbers

  • Atomic number = number of protons.

  • Mass number = number of protons + number of neutrons.

  • Isotopes: Atoms of the same element differing in neutron count, thus differing in mass but not in chemical properties.