Chapter 4: Atomic Structure and the Periodic Table

Elemental Symbols and the Periodic Table

The periodic table organizes elements by increasing atomic number and groups elements with similar chemical properties. Each element is represented by a unique symbol.

• Elemental Symbols: One- or two-letter abbreviations for each element (e.g., H for hydrogen, O for oxygen).

• Groups and Periods: Groups are vertical columns; periods are horizontal rows.

• Metals, Nonmetals, Metalloids: Elements are classified based on their properties and position on the table.

• Periodic Trends: Properties such as atomic radius, ionization energy, and electronegativity change predictably across periods and groups.

Example: Sodium (Na) is a metal in Group 1, Period 3.

Subatomic Particles and Atomic Structure

Atoms consist of protons, neutrons, and electrons. Their arrangement determines the atom's properties.

• Atomic Number: Number of protons in the nucleus ().

• Mass Number: Total number of protons and neutrons ().

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Electron Arrangements: Electrons occupy energy levels or shells around the nucleus.

• Valence Electrons: Electrons in the outermost shell, important for chemical bonding.

Formula:

where is mass number, is atomic number, and is number of neutrons.

Chapter 5: Radiation and Nuclear Chemistry

Types of Radiation

Radioactive decay involves the emission of particles or energy from unstable nuclei.

• Alpha Particles: Helium nuclei (), low penetration.

• Beta Particles: Electrons (), moderate penetration.

• Gamma Rays: High-energy electromagnetic radiation, high penetration.

• Positrons: Positive electrons ().

Example: (beta decay)

Biological Effects and Protection from Radiation

Radiation can damage biological tissues; safety measures are essential.

• Shielding: Lead, concrete, or other materials reduce exposure.

• Radiation Measurement: Units include rad, rem, and sievert (Sv).

• OSHA Limit: Maximum safe exposure for workers.

• Half-Life: Time required for half of a radioactive sample to decay.

Formula:

where is remaining nuclei, is initial amount, is decay constant, is time.

Medical Applications and Nuclear Reactions

Radioisotopes are used in medical imaging and treatment. Nuclear reactions include fission and fusion.

• PET, MRI, CT: Imaging techniques using radioisotopes.

• Fusion: Combining nuclei to form a heavier nucleus.

• Fission: Splitting a heavy nucleus into lighter nuclei.

Example: (fission)

Chapter 6: Chemical Bonding and Molecular Structure

Ions and Ionic Compounds

Ions are charged particles formed by the loss or gain of electrons. Ionic compounds consist of positive and negative ions held together by electrostatic forces.

• Cations: Positively charged ions (loss of electrons).

• Anions: Negatively charged ions (gain of electrons).

• Naming Ionic Compounds: Name cation first, then anion (e.g., sodium chloride).

• Polyatomic Ions: Ions composed of multiple atoms (e.g., SO42-).

Formula:

Covalent Bonding and Molecular Structure

Covalent bonds involve the sharing of electrons between nonmetal atoms. Molecular structure affects physical and chemical properties.

• Single, Double, Triple Bonds: Sharing one, two, or three pairs of electrons.

• Lewis Structures: Diagrams showing bonding and lone pairs.

• Bond Polarity: Difference in electronegativity creates polar or nonpolar bonds.

• VSEPR Theory: Predicts molecular shapes based on electron pair repulsion.

Example: Water (H2O) has a bent shape due to two lone pairs on oxygen.

Intermolecular Forces and Physical Properties

Intermolecular forces determine boiling points, melting points, and solubility.

• Dipole-Dipole Interactions: Attraction between polar molecules.

• Dispersion Forces: Weak forces present in all molecules.

• Hydrogen Bonding: Strong attraction involving H and N, O, or F.

• Melting and Boiling Points: Influenced by strength of intermolecular forces.

Example: Water has a high boiling point due to hydrogen bonding.

Table: Comparison of Bond Types

Additional info: Some context and explanations have been expanded for clarity and completeness based on standard GOB Chemistry curriculum.