(2) GCSE Physics - Atomic Structure, Isotopes & Electrons Shells #32

Overview of Atoms

• The video covers the essential information regarding atomic structure and isotopes, along with electron movement between energy levels.

Structure of an Atom

• Nucleus: Center of the atom, containing protons and neutrons.

  • Protons: Positively charged (+1), each with a relative mass of 1.

  • Neutrons: Neutral charge, also with a relative mass of 1.

• Electrons: Orbit the nucleus in shells, much smaller than protons and neutrons (about 2,000 times smaller), with a negative charge (-1).

Understanding the Periodic Table

• Each box in the periodic table is a nuclear symbol representing an element.

  • Elemental Symbol: Shown at the top right (e.g., Li for lithium).

  • Atomic Number: Bottom left number, indicates the number of protons and determines the element. For lithium, this is 3.

  • Mass Number: Top left number, total of protons and neutrons. Lithium's mass number is 7 (3 protons + 4 neutrons).

• Electrons: The number of electrons in a neutral atom equals the number of protons. Lithium has 3 electrons.

Isotopes

• Definition: Atoms of the same element with the same number of protons (atomic number) but different numbers of neutrons (mass numbers).

  • Examples:

    • Lithium-7: 3 protons, 4 neutrons.

    • Lithium-6: 3 protons, 3 neutrons.

    • Lithium-8: 3 protons, 5 neutrons.

• Stability: Most elements have one or two stable isotopes; others are unstable and can undergo radioactive decay, emitting radiation (alpha, beta, or gamma).

Electron Energy Levels

• Energy Levels (Shells): Electrons are arranged in shells around the nucleus, with each successive shell being further away and having higher energy.

• Electron Excitation: Electrons can jump to a higher energy level if enough energy is absorbed (from electromagnetic radiation). This is known as excitation.

• Emission: Electrons typically return to their original shell, emitting energy as electromagnetic radiation.

Ionization

• Ionization Process: Occasionally an outer electron absorbs so much energy that it leaves the atom entirely.

  • This creates a positive ion due to the surplus of protons (more protons than electrons).

• Ionizing Radiation: This term refers to radiation that can knock electrons off atoms, resulting in ionization.

Conclusion

• The video provides an overview of atomic structure, isotopes, and electron energy levels, preparing viewers for the next topic on radioactive decay.