chemistry

Chemistry Overview

• Chemistry is defined as the study of the smallest forms of matter, specifically atoms and molecules.
• Matter refers to anything that has mass and occupies space.
• To conceptualize matter, it is useful to consider what it is not: thoughts, feelings, ideas, emotions, and color.

Definition of Matter

• Matter encompasses everything with a physical presence, regardless of size.
• Atoms are the smallest units of matter that possess unique properties.
• Smaller forms of matter exist but do not exhibit the diverse characteristics recognized in observable matter.
  • Example: A hydrogen atom - its diameter is remarkably 173,000,000 times smaller than a penny.

Subatomic Particles

• Atoms consist of smaller particles called subatomic particles, the details of which will be covered later.

Elements and Atoms

• There are approximately 90 naturally occurring varieties of atoms known as elements.
• Each element has a name (e.g., carbon, helium, sodium, uranium) and a corresponding symbol (e.g., C for carbon, Na for sodium).

Common Elements in the Human Body

• The most abundant elements in the human body include:
  • Oxygen
  • Carbon
  • Hydrogen
  • Nitrogen
  • Calcium
  • Phosphorus
  • Potassium
  • Sodium
  • Iron

The Periodic Table

• The periodic table systematically organizes all known elements based on their properties and similarities.
• Key information from the periodic table includes:
  • Atomic Number: Number of protons in an atom's nucleus.
  • Atomic Mass: Total number of protons and neutrons.

Atomic Structure

• An atom is composed of three main subatomic particles:
  1. Protons
  • Located in the nucleus.
  • Positive charge.
  • Mass of 1 atomic mass unit (1 AMU).
  1. Neutrons
  • Also in the nucleus.
  • No electrical charge.
  • Mass comparable to protons (1 AMU).
  1. Electrons
  • Orbit the nucleus at specific distances (energy levels).
  • Negative charge.
  • Insignificant mass compared to protons and neutrons.

Atomic Properties

• Atomic Number: Unique identifier for an element. All atoms of a specific element have the same number of protons.
• Atomic Mass: Calculated as the sum of protons and neutrons; does not include electron mass because it is negligible.
• Example: For boron, atomic number = 5 (5 protons), atomic mass rounded to 11, meaning typically 6 neutrons (11 - 5 = 6).

Electron Configuration

• Electrons reside at specific energy levels:
  • Energy Level 1 can hold up to 2 electrons.
  • Energy Levels 2 through 7 can accommodate a maximum of 8 electrons each.
  • Example: For an atom with 11 electrons:
  • 2 in Level 1
  • 8 in Level 2
  • 1 in Level 3
• Valence Electrons: Outermost electrons involved in chemical reactions.
• An atom is neutral when it has an equal number of protons and electrons.

Stability and Chemical Behavior

• Atoms strive to achieve a full outermost energy level for stability, which may involve:
  • Gaining electrons to form anions (negatively charged).
  • Losing electrons to form cations (positively charged).

Molecular Formation

• Molecule: A combination of two or more atoms bonded together.
• Bonding occurs through forces such as:
  • Ionic Bonds: Result from the attraction between oppositely charged ions (e.g., anions and cations).
  • Covalent Bonds: Formed when atoms share electrons to achieve stability; these bonds are stronger than ionic bonds.
  • Hydrogen Bonds: Weak attractions between partially charged atoms in different molecules.

Solutions and Mixtures

• Solute: A substance introduced into a liquid (solvent) to create a mixture.
• Solvent: The liquid in which the solute is mixed.
• Solution: The resultant homogeneous mixture of solute and solvent.
  • Requires certain properties to qualify as a solution: solute size comparable to solvent size, transparency, ability to pass through membranes, stability without settlement.

Electrolytes and pH

• Electrolyte: Molecules that dissociate into ions in solution (e.g., NaCl dissolves into Na⁺ and Cl⁻).
• Essential for nerve and muscle functions.
• Common ions: Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻.

Acids and Bases

• Acids: Electrolytes that release hydrogen ions (H⁺) in water (e.g., HCl → H⁺ + Cl⁻).
• Bases: Electrolytes that accept H⁺ ions in water.
• The pH Scale:
  • Measures the concentration of free H⁺ ions.
  • Scale ranges from 0 (high acidity) to 14 (high basicity), with 7 being neutral.

Organic and Inorganic Molecules

• Organic Molecules: Contain carbon and play a primary role in biological systems; examples include proteins, carbohydrates, lipids, nucleic acids, and ATP.
• Inorganic Molecules: Do not contain carbon.

Key Organic Molecules

• Carbohydrates:

  • Known as sugars and starches; primary energy sources.
  • Basic formula: C₆H₁₂O₆ (glucose).
  • Types:
  • Monosaccharides: Simplest form (e.g., glucose, galactose, fructose).
  • Disaccharides: Two monosaccharides bonded (e.g., sucrose, lactose).
  • Polysaccharides: Long chains (e.g., starch, cellulose, glycogen).

• Lipids:

  • Composed of carbon, hydrogen, and oxygen; primarily hydrophobic.
  • Types:
  • Fatty Acids: Linear chains of carbon atoms.
    • Saturated: All bonds filled with hydrogen.
    • Unsaturated: Involves double bonds between carbon atoms.
  • Triglycerides: Three fatty acids attached to glycerol (energy storage).
  • Phospholipids: Two fatty acids and a phosphate group; vital for cell membranes.
  • Steroids: Four fused carbon rings; cholesterol is a notable example.

• Proteins:

  • Composed of carbon, hydrogen, oxygen, nitrogen; made of amino acids.
  • Functions include:
  • Structure (e.g., keratin, collagen).
  • Communication (e.g., receptors).
  • Catalysis (e.g., enzymes).
  • Protection (e.g., antibodies).
  • Movement (e.g., actin, myosin).

• Nucleic Acids:

  • DNA: Carries genetic information.
  • RNA: Involved in protein synthesis.

• ATP (Adenosine Triphosphate):

  • Main energy currency for cells; comprises an adenosine molecule with three phosphate groups.
  • Most energy stored between the second and third phosphate groups.