Atomic Structure and Radioactivity

Atomic Structure and Radioactivity Notes

Building Blocks of Matter

• All materials are made of tiny building blocks known as atoms.

Atomic Structure

Atoms

• Definition: Atoms are the smallest units of an element that retain the properties of that element.

• Components:

  • Nucleus: Contains protons and neutrons.

  • Electrons: Orbit the nucleus in regions known as electron shells or energy levels.

Electron Configuration

• Definition: The arrangement of electrons in each energy level around the nucleus.

• Key Points:

  • Electrons fill the closest shell to the nucleus first before occupying outer shells.

  • Maximum electrons in a shell: Given by the formula $ext{Max Electrons} = 2n^2$, where n is the shell number.

  • For elements 1-20, the typical filling order is:

  • First shell: 2 electrons

  • Second shell: 8 electrons

  • Third shell: 8 electrons

  • Fourth shell: 2 electrons

Visual Representation of Atoms

• Sketch example: Carbon Atom

  • Protons: 6

  • Neutrons: 6

  • Electrons: 6

Electron Shell Filling

• Shells can hold the following maximum electrons:

  • 1st Shell: 2 electrons

  • 2nd Shell: 8 electrons

  • 3rd Shell: typically 18, but effectively fills as 8 for the first 20 elements.

  • 4th Shell: 32 electrons

Properties of Subatomic Particles

Periodic Table of Elements

• Definition: A table listing elements in order of increasing atomic number (number of protons).

• Elements: Total of 118 known elements, with 91 naturally occurring on Earth.

Determining Element Identity

• Atomic Number: Number of protons in an atom.

• Mass Number: Total number of protons and neutrons.

• For example, Oxygen has 8 protons (atomic number 8).

Finding Subatomic Particles

• General Relations:

  • For a neutral atom: Number of protons = Number of electrons.

  • Number of neutrons = Mass number - Atomic number.

• Example Calculation:

  • For an atom with 5 protons and 5 neutrons:

  • Mass number: 5 (protons) + 5 (neutrons) = 10

  • Atomic number: 5

Isotopes

• Definition: Variations of the same element with the same number of protons but a different number of neutrons.

• Isotope Naming: Generally named as Element-Mass Number (e.g., Carbon-12 is $^{12}C$, Carbon-13 is $^{13}C$).

• Examples of Chlorine Isotopes:

  • $^{35}Cl$: 17 protons, 18 neutrons.

  • $^{37}Cl$: 17 protons, 20 neutrons.

Radioisotopes

• Definition: Unstable isotopes that release radiation during decay.

• Types of Decay:

  • Alpha Decay: Emission of alpha particles (helium nuclei), can be stopped by paper.

  • Beta Decay: Emission of beta particles (electrons), can be stopped by aluminum or plastic.

  • Gamma Decay: Emission of gamma rays (no mass), very penetrating, occurs to stabilize the nucleus.

• Common Radioisotope Examples:

  • Cobalt-60: Used in cancer treatment.

  • Iodine-131: Used as a tracer and in thyroid treatment.

  • Carbon-14: Used in carbon dating.

Half-life

• Definition: Time taken for half of the radioactive material to decay.

• Examples of Half-lives:

  • Carbon-14: 5,730 years.

  • Iodine-131: 8.02 days.

  • Cobalt-57: 271.79 days.

Applications of Half-life

• Carbon Dating: Age determination of organic material based on carbon-14's half-life.

• Medical Applications: Includes diagnostic nuclear medicine and therapeutic approaches like radiation therapy.

Review Activities

• Engage in activities to reinforce knowledge (e.g., Kahoot, Frayer models, partner discussions).

• Glossary Terms to Explore: Define terms like isotope, atomic number, and radioactivity with examples and non-examples to deepen understanding.