Periodic Table

Focus on "basic-ish" chemistry relating to the human body
Questions to gauge student comfort with chemistry.
Chemistry defined:
- Matter: Anything that occupies space and has mass.
- Examples: Pencil, paper, air, atoms.

Three states of matter:
- Solids:
- Maintain shape, do not expand, can be contained (e.g., a pencil stays in form in a jar).
- Liquids:
- Take the shape of their container but do not expand (e.g., water fills a glass).
- Gases:
- Expand to fill their container (e.g., air), can be visible or invisible.

Atoms: Smallest components of elements, composed of:
- Nucleus:
- Contains protons (positive charge).
- Contains neutrons (no charge).
- Electrons:
- Surround the nucleus, have negative charge.

Naturally Occurring Elements: 92, with additional man-made elements.
- Common elements in the human body highlighted.
Each element on the periodic table has:
- Atomic number: Number of protons.
- Chemical symbol: Symbol representing the element (e.g., H for hydrogen).
- Atomic mass: Average mass of an atom (e.g., 1.008 for hydrogen).

Oxygen (65% body weight)
- Vital for energy and biological processes.
Carbon (18.5% body weight)
- Foundation for fats, proteins, DNA, carbohydrates.
Hydrogen (9.5% body weight)
- Key in water and chemical reactions (e.g., pH regulation).
Nitrogen (3% body weight)
- Component of proteins and nucleic acids (DNA).
Calcium
- Crucial for bone structure and cell signaling.
Phosphorus
- Important for DNA structure.
Minor Elements:
- Sulfur: Found in proteins.
- Potassium, Sodium, Chlorine: Essential for neurotransmission & cell communication.
- Magnesium: Regulates blood pressure.
- Iron: Critical for hemoglobin in blood.

Models of atom: Two representations discussed:
- Common simplified model vs. realistic probability cloud model.
Neutrons: No charge, contributes to atomic weight.
Protons: Positive charge, defines the element.
Electrons: Negative charge, found in a cloud surrounding the nucleus.

Changes in the number of neutrons lead to radioactivity.
- Unstable isotopes decay over time, releasing particles (alpha, beta, gamma).
- Alpha particles: Weak penetration.
- Beta particles: Moderate penetration.
- Gamma radiation: High penetration, dangerous.
Isotopes: Variants of elements with different neutron counts (e.g., Carbon-12, Carbon-13, Carbon-14).
- Half-life: Time needed for half of a radioactive substance to decay.
- Example: If half-life is 3 minutes, after 3 minutes, 50% remains.
- Biological half-life: Time for body to eliminate a substance.

Valence Shells:
- Atoms desire to fill their outer shells (octet rule - usually 8 electrons).
Types of Bonds:
- Ionic Bonds: Atoms transfer electrons (e.g., Sodium gives an electron to Chlorine)
  - Creates positive ions (cations) and negative ions (anions).
- Covalent Bonds: Atoms share electrons.
  - Sharing can be equal or unequal, forming polar or nonpolar molecules.

Defined as how likely an element is to gain or lose electrons in bonding.
Elements located higher and to the right in the periodic table are more electronegative.

Use elemental symbols correctly (e.g., H for Hydrogen, Cl for Chlorine).
Chemical formulas show element composition and how many atoms are involved (e.g., H2O).
Multiple valid ways to write some chemical formulas (e.g., calcum hydroxide).

Visual representation of electrons in atoms.
Illustrate how atoms bond by sharing electrons, also demonstrating octets.
Example with water (H2O): 1 Oxygen and 2 Hydrogens share electrons to complete their valence shells.

Students prepared to practice drawing structures, including Lewis and skeletal structures in upcoming classes.
Emphasis on the importance of understanding electron distribution in bonding.