Chemistry Class: Atomic Structure and Elements

Elements Comprising the Human Body

• Three elements make up 90% of human body mass: oxygen, carbon, and hydrogen.
• Oxygen is crucial for respiration and metabolic processes.

Dalton’s Atomic Theory (1808)

• All matter is composed of tiny indivisible particles called atoms.
• Atoms of the same element are identical; atoms of different elements vary.
• Atoms can combine to form molecules.
• Law of Conservation of Mass: mass can neither be created nor destroyed but can be rearranged.

Atomic Structure

• Neutral atoms identified by the number of protons and neutrons.
• Charged particles:
  • Electron: mass of 9.109 × 10−31 kg, charge of -1.
  • Proton: mass of 1.673 × 10−27 kg, charge of +1.
  • Neutron: mass of 1.675 × 10−27 kg, no charge.
• Charge magnitude for protons and electrons is 1.60 × 10−19 C.

Atomic Number and Mass Number

• Proton Number (Z): number of protons in an atom's nucleus, defining the element.
• Nucleon Number (A): total protons and neutrons in an atom's nucleus, known as mass number.

Isotopes

• Isotopes: atoms of the same element with identical proton numbers but different nucleon numbers.
• React identically in chemical reactions due to the same electron configuration.
• Exhibit different physical properties (mass, speed, boiling/melting points).
  • Example: Protium (1H) vs. Deuterium (2H).
  • Heavy water (D2O) has distinct physical properties, including a higher boiling point.

Isotope Properties

• Isotopes with fewer neutrons have:
  • Lower masses and densities.
  • Higher diffusion rates and lower melting/boiling points.

Understanding Isotopes

• Example:
  • Carbon-14 (¹⁴C): 6 protons, 8 neutrons, 6 electrons.
  • Carbon-11 (¹¹C): 6 protons, 5 neutrons, 6 electrons.

Statements about Atoms

• True statements regarding neutral atoms:
  • I: Number of protons is constant in neutral atoms of an element.
  • II: Number of electrons is constant in neutral atoms of an element.
  • III: Number of neutrons may vary (not constant for isotopes).

Mass Spectrum of Lead and Magnesium

• Mass spectrum provides isotopic distribution and relative abundance.
• Example of lead isotopes with relative abundances.
• Magnesium has three isotopes: ²⁴Mg, ²⁵Mg, ²⁶Mg, with ²⁴Mg being the most common.

Relative Atomic Mass Calculation

• Relative atomic mass can be calculated from isotopic abundances using mass spectrum data to determine average atomic weight.

Explore the fundamental concepts of atomic structure and the elements that comprise the human body. This quiz covers Dalton’s Atomic Theory, the importance of oxygen, carbon, and hydrogen, and the characteristics of protons, neutrons, and electrons. Test your understanding of how these elements and particles interact.