Atomic Structure and Composition Quiz

Atomic Structure and Components

• Atoms consist of negatively charged electrons orbiting a positively charged nucleus.
• The nucleus contains protons (positively charged) and neutrons (uncharged), contributing to the atom's mass.
• Protons: Charge +1.6 × 10^-19 C, Mass 1.673 × 10^-27 kg
• Neutrons: Charge 0, Mass 1.675 × 10^-27 kg
• Electrons: Charge -1.6 × 10^-19 C, Mass 9.1 × 10^-31 kg

Atomic Mass and Composition

• Protons and neutrons (nucleons) define the atomic mass unit (amu), with 1 amu equal to 1/12 of a C-12 atom's mass.
• Mass values:
  • Electron: 0.000549 amu
  • Proton: 1.00728 amu
  • Neutron: 1.00867 amu
• Atomic mass number ( A ) refers to the total number of nucleons (protons + neutrons).

Electron Shells and Binding Energy

• Electrons occupy energy levels or shells designated as K, L, M, N, etc.
• Maximum electron capacity per shell: K (2), L (8), M (18), N (32).
• Electron binding energy (BEe) is the energy needed to remove an electron, typically starting around 5 eV.

Ionization Process

• Ionization involves removing or adding electrons to an atom, often through exposure to X-rays.
• Post-ionization, an atom will have a net charge; e.g., a carbon atom becomes +1 after losing an electron, forming an ion pair.

Atomic Nomenclature

• Chemical symbols represent elements and their atomic numbers (Z).
• Example notation: ( ^{135}_{56}Ba ) implies a mass number (A) of 135 and atomic number (Z) of 56, indicating 79 neutrons.
• Other formats include Ba-135 for ease of identification.

Isotopes, Isobars, Isotones, and Isomers

• Isotopes share the same Z but have different neutron counts (e.g., I-130 and I-131).
• Isobars have the same mass number but differ in atomic number (e.g., I-131 and Xe-131).
• Isotones have the same number of neutrons but different mass numbers (e.g., I-130 and Xe-131).
• Isomers have identical Z and A but exist in different energy states (e.g., Tc-99 and Tc-99m).

Molecular Structures

• A molecule consists of atoms bonded in a fixed ratio (e.g., NaCl).
• Types of bonds include:
  • Covalent (sharing electrons).
  • Ionic (transfer of electrons).

Learning Outcomes and Themes

• Understand the evolution of atomic models from early Greek theories to the Bohr model.
• Define key atomic concepts: electrons, protons, neutrons, atomic mass units, and atomic structures.
• Grasp the fundamentals of radioactivity, including alpha and beta particles, as well as differences between particle and electromagnetic radiation.

Learning Outcomes

• Understand the historical evolution of atomic models.
• Recognize the current structure of the atom.
• Explain electron shells and the concepts of atomic stability and instability.
• Discuss radioactivity, particularly characteristics of alpha and beta particles.
• Differentiate between particulate and electromagnetic forms of ionizing radiation.

Atomic Basics

• Atoms are the fundamental building blocks of matter.
• Approximately 118 known elements, with 26 artificially produced and 92 occurring naturally.
• Mendeleev's Periodic Table dates back to the 1860s.

Bohr Model

• The Bohr model (1913) describes electrons in fixed circular orbits around a nucleus.
• Electrons are negatively charged; the nucleus contains positively charged protons and uncharged neutrons.

Atomic Particles

• Electrons: Charge = -1.6 × 10⁻¹⁹ C; Mass = 9.1 × 10⁻³¹ kg.
• Protons: Charge = +1.6 × 10⁻¹⁹ C; Mass = 1.673 × 10⁻²⁷ kg.
• Neutrons: Charge = 0; Mass = 1.675 × 10⁻²⁷ kg.

Atomic Mass and Nomenclature

• Protons and neutrons are called nucleons; the atomic mass unit (amu) is defined as 1/12 the mass of a C-12 atom.
• Atomic mass numbers (A) indicate total nucleons; they align with protons (Z) and signify chemistry.
• Isotopes share the same Z but differ in neutron number (N).

Electron Shells

• Electrons are organized in shells: K (2), L (8), M (18), N (32) - filled shells denote stability.
• Electron binding energy (BE) is the energy necessary for ionization.

Ionization

• Ionization occurs when electrons are removed or added, forming ions with electric charges.
• X-rays can ionize atoms, highlighting their role as ionizing radiation.

Atomic Symbols

• Chemical symbols represent elements, with notation including subscript (Z) for atomic number and superscript (A) for atomic mass.
• For example, barium can be denoted as 135Ba₅₆ or Ba-135.

Isotopes, Isobars, Isotones, and Isomers

• Isotopes: Same Z, different N (e.g., I-130 and I-131).
• Isobars: Same A, different Z (e.g., I-131 and Xe-131).
• Isotones: Same N, different A (e.g., I-130 and Xe-131).
• Isomers: Same Z and A, different energy states (e.g., Tc-99 and Tc-99m).

Molecular Structure

• Molecules are formed from atoms in fixed ratios, like NaCl.
• Types of bonding include covalent and ionic bonds.

Summary of Key Concepts

• Familiarize with terms: electron, proton, neutron, atomic number, mass number, atomic mass unit.
• Review atomic arrangements, periodic table structure, radioactivity, and properties of alpha and beta particles.