Atoms and Elements

Levels of Structural Organization in the Human Body

• The human body is organized into six distinct hierarchical levels. According to the course material, students must KNOW THE SIX LEVELS:

  • CHEMICAL LEVEL: This represents the basic building blocks of chemistry.

    • Atoms: High-level examples include Hydrogen ($H$) and Carbon ($C$).

    • Molecules: Combinations of atoms, such as a Phospholipid molecule.

  • CELLULAR LEVEL: The level where molecules form functional units within a cell.

    • Key components include the Cell membrane and specific cell types like the Squamous epithelial cell.

  • TISSUE LEVEL: Groups of similar cells that collaborate to perform a specific function.

    • The example provided is Stratified squamous epithelium (Figure $4$).

  • ORGAN LEVEL: Different tissue types integrated to perform a complex physiological function.

    • The specific example illustrated is the Esophagus.

  • ORGAN SYSTEM LEVEL: Groups of organs working together for a common purpose.

    • The example provided is the Digestive system.

  • ORGANISM LEVEL: The highest level, representing the human being as a single whole functioning unit.

Elements and the Human Periodic Table

• Composition of the Human Body: Elements in the human body are categorized by their relative abundance (Figure $2.2$):

  • Major Elements ($96\%$): The primary contributors to body mass.

  • Mineral Elements (<4\%): Essential elements found in smaller quantities.

  • Trace Elements ($0.01\%$): Present in very small, yet vital, amounts.

• Periodic Table Classifications:

  • The table distinguishes between Metals and Nonmetals.

  • Rare Earth Elements: These are explicitly identified as elements not found in the human body.

• Rules for Atomic Symbols:

  • Every element is represented by an Atomic Symbol.

  • If a symbol contains two letters, the first letter must be capitalized and the second letter must be lower-case (e.g., Sodium is $Na$, not $NA$ or $na$).

Atomic Structure and Models

• Atoms: Known as the "Building blocks" of chemistry.

• Subatomic Particles (Figure $1$):

  • Protons ($p^+$): Found in the nucleus; they possess a Positive electrical charge.

  • Neutrons ($n^0$): Found in the nucleus; they have No charge (neutral).

  • Electrons ($e^-$): Spin around the nucleus in specific energy levels (shells); they possess a Negative electrical charge.

• Balance of Charge: In a standard atom, the number of protons and electrons is usually the same, ensuring electrical neutrality. However, the number of neutrons is typically not equal to the number of protons.

• Visualizing Atomic Structure (Figure $2.3$):

  • Planetary Model: Portrays electrons in fixed orbits or rings at a precise distance from the nucleus. This is exemplified by the structure of Helium ($He$).

  • Electron Cloud Model: Portrays electrons in a variety of locations they might occupy at different distances from the nucleus over time. This is exemplified by Carbon ($C$).

Periodic Table Data and Calculations

• A periodic table entry (e.g., $_6^{12}C$) provides specific quantitative data:

  • Atomic Number: Represents the number of protons. This number is crucial as it identifies the type of element.

  • Atomic Mass: Represents the sum of protons and neutrons within the nucleus.

  • Atomic Symbol: Indicates the specific type of element.

• Calculation Practice (Sub-Atomic Particles):

  • To find Neutrons, subtract the Atomic Number from the Atomic Mass: $n = \text{Atomic Mass} - p$.

  • Oxygen ($O$): $Atomic\,Number = 8, Mass = 16 \rightarrow p = 8, n = 8, e = 8$.

  • Phosphorus ($P$): $Atomic\,Number = 15, Mass = 31 \rightarrow p = 15, n = 16, e = 15$.

  • Chlorine ($Cl$): $Atomic\,Number = 17, Mass = 35 \rightarrow p = 17, n = 18, e = 17$.

  • Sulfur ($S$): $Atomic\,Number = 16, Mass = 33 \rightarrow p = 16, n = 17, e = 16$.

  • Calcium ($Ca$): $Atomic\,Number = 20, Mass = 40 \rightarrow p = 20, n = 20, e = 20$.

Drawing and Representing Atoms

• Step-by-Step Procedure for Drawing Atomic Structure:

  1. Determine the specific number of each subatomic particle ($p, n, e$).

  2. Draw the nucleus and label it with the number of protons and neutrons.

  3. Draw the $1^{st}$ energy level; insert a maximum of $2$ electrons.

  4. Draw the $2^{nd}$ energy level; insert a maximum of $8$ electrons.

  5. Continue adding energy levels ($3^{rd}$ level also holds $8$) until all electrons are placed.

• Sample Drawing Data:

  • Carbon ($C$) ($Atomic\,Number\,6, Mass\,12$): Nucleus contains $6p$ and $6n$. Electrons are distributed with $2$ in the first shell and $4$ in the second shell.

  • Sodium ($Na$) ($Atomic\,Number\,11, Mass\,23$): Nucleus contains $11p$ and $12n$. Electrons are distributed with $2$ in the first shell, $8$ in the second shell, and $1$ in the third shell.

Valence Electrons and Vacancy Numbers

• Definitions:

  • Valence Electrons: The count of electrons located in the outermost energy level of the atom.

  • Vacancy Number: The number of open spaces remaining in the outer level to reach its maximum capacity.

• Calculation Rules:

  • $1^{st}$ Energy Level: Maximum of $2$ electrons.

  • $2^{nd}$ & $3^{rd}$ Energy Levels: Maximum of $8$ electrons.

• Procedure for Determining Valence/Vacancy Values:

  1. Identify the total number of electrons ($e^-$).

  2. Fill levels sequentially ($2, 8, 8$).

  3. Identify the count in the outer level (Valence).

  4. Subtract the valence number from the level's maximum (Vacancy).

• Example: Potassium ($K$) ($Atomic\,Number\,19$):

  • Total $e^- = 19$.

  • Level $1 = 2$ electrons ($17$ remain).

  • Level $2 = 8$ electrons ($9$ remain).

  • Level $3 = 8$ electrons ($1$ remains).

  • Level $4 = 1$ electron (This is the outermost level).

  • Valence electrons = $1$.

  • Vacancies = $8 - 1 = 7$ (Assuming fourth level max mirrors third level capacities for introductory purposes).

• Class Activity Data for Valence/Vacancy:

  • Helium ($He$) ($Mass\,4$): Valence = $2$, Vacancies = $0$.

  • Magnesium ($Mg$) ($Mass\,24$): Valence = $2$, Vacancies = $6$.

  • Phosphorus ($P$) ($Mass\,31$): Valence = $5$, Vacancies = $3$.