Atoms and Subatomic Particles

Fundamental Concepts of Atoms

Definition of Atoms

  • Atoms are the smallest particle of an element.

    • They consist of:

    • A nucleus made up of protons and neutrons.

    • A cloud of electrons surrounding the nucleus.

Structure of Atoms

  • Nucleus: Central part of the atom.

    • Contains:

    • Protons: Large subatomic particles with a positive charge.

    • Neutrons: Large subatomic particles with no charge (neutral).

  • Electrons: Very small subatomic particles with a negative charge.

    • Located outside the nucleus in an electron cloud.

Atomic Properties

  • Atomic Number: The number of protons in each atom of an element; unique to each element.

    • In neutral atoms, this is also the number of electrons.

  • Mass Number: The total number of protons and neutrons in an atom; can vary among atoms of the same element due to differing neutron counts.

Electron Cloud Model

  • Electron Cloud Model: Describes the behavior of electrons within an atom.

    • In this model, electrons move freely and may be located anywhere in the electron cloud at any time.

Ions and Charges

  • Ion: An atom or molecule with a net charge.

    • Negative Ion: A neutral atom that gains an electron, resulting in a charge of -1.

    • Positive Ion: An atom or molecule with a net positive charge, which occurs when it has more protons than electrons.

    • Neutral Atom: Has an equal number of protons and electrons.

Isotopes

  • Isotope: Variations of an element that differ in the number of neutrons.

    • Carbon-14: An unstable isotope of carbon with two more neutrons than Carbon-12, making it prone to radioactive decay.

    • Carbon-12: A stable isotope of carbon that consists of equal numbers of protons and neutrons.

Radiation and Decay

  • Radioactive Decay: The process by which unstable atoms release radiation to stabilize their nucleus.

    • Types of Radiation:

    • Alpha Particles: Positively charged particles ejected during decay.

    • Beta Particles: High-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei.

    • Gamma Waves: High-frequency electromagnetic radiation emitted during radioactive decay.

Key Terms

  • Subatomic Particle: A particle smaller than an atom (includes protons, neutrons, and electrons).

  • Stable Isotope: An isotope that does not break apart easily.

  • Unstable Isotope: An isotope likely to break apart and release radiation due to an excess in neutron count.

Summary of Charge Properties

  • Atoms can exhibit:

    • Positive Charge: More protons than electrons.

    • Negative Charge: More electrons than protons.

    • Neutral Charge: Equal number of protons and electrons.

  • Net Charge: The overall electrical charge of a particle defined by the formula:
    \text{Net Charge} = \text{Number of Protons} - \text{Number of Electrons}

Models of Atom

  • Planetary Model: An early model of the atom where electrons circle the nucleus in defined orbits, akin to planets orbiting the sun.