Chemical Level of Organization Notes

Matter and Mass

• Matter: Anything with mass that occupies space.
• Mass: The quantity of matter in an object, a physical property that determines weight in Earth's gravitational field. For this course, mass is considered the same as weight, although they are not always equivalent.

States of Matter

• Solid: Definite shape and volume.
• Liquid: Definite volume, changeable shape.
• Gas: Changeable shape and volume.
• Water: Exists in all three states (ice, water, water vapor) at life-compatible temperatures.

Elements and Their Properties

• Elements: Cannot be broken down by ordinary chemical means; possess unique physical and chemical properties.
• Physical Properties: Detectable with senses and measurable.
• Chemical Properties: How atoms interact or bond.
• Each element has a unique chemical symbol (e.g., Oxygen is O, Carbon is C, Calcium is Ca, Potassium is K).

Elements in the Human Body

• Principal Elements (most abundant):
  • Oxygen, Carbon, Hydrogen, Nitrogen
• Lesser Elements:
  • Calcium, Phosphorus, Potassium, Sulfur, Sodium, Chlorine, Magnesium, Iodine, Iron
• Trace Elements (less than 0.01%):
  • Often part of enzymes (e.g., Zinc, Chromium, Manganese)

Atoms and Molecules

• Atoms: Smallest stable units of matter, composed of subatomic particles.
• Subatomic Particles:
  • Neutrons: No charge.
  • Protons: Positive charge (in the nucleus).
  • Electrons: Negative charge, orbit the nucleus (equal in number to protons in a balanced atom).
• Atomic Structure Models:
  • Planetary Model
  • Electron Cloud Model (electrons in shells)
• Electrons participate in chemical reactions.
• Molecules: Larger, complex structures formed when atoms interact.

Atomic Number, Mass Number, and Isotopes

• Atomic Number: Number of protons in a nucleus.
• Mass Number: Mass of protons and neutrons.
• Atomic Weight: Average of mass numbers of all isotopes.
• Isotopes: Atoms with the same number of protons but different numbers of neutrons; identical chemical properties but different mass numbers.
• Radioactive Isotopes: Spontaneously decay; used in research and medicine but can damage living tissue. Useful against localized cancer.
• Atomic Weight Unit: Daltons (one Dalton ≈ weight of one proton or neutron).
• Example: Hydrogen has an atomic number of 1, a mass number of 1, and an atomic weight slightly more than 1, reflecting isotope proportions.

PET Scan

• PET Scan Use: Highlights different areas in the body to look for, for example, areas that have high glucose use.
• PET Scan and Cancer: Glucose is a preferential food source for cancer.
• PET Scan Application: Can be used to identify and track the spread of tumors.

Electrical Charge and Energy Levels

• Atoms are electrically neutral (positive protons balanced by negative electrons).
• Electrons occupy different energy levels (shells).
• Outermost Shell (Valence Shell): Determines chemical properties.
• Atoms with unfilled outer shells are reactive (electrons want to pair).
• Atoms with full outer shells are inert (stable, do not readily react) - Noble gases.

Ions

• Ions: Charged atoms (cations or anions).
• Cations: Atoms that have lost electrons, resulting in a net positive charge (e.g., Sodium atom losing an electron to form a sodium cation).
• Anions: Atoms that have gained electrons, resulting in a net negative charge (e.g., Chlorine gaining an electron).

Molecules vs. Compounds

• Molecules: Chemical substance consisting of atoms of one or more elements held together by covalent bonds.
• Compounds: Chemical substance made up of two or more atoms from different elements.
• Both participate in chemical reactions.

Chemical Bonds

• Ionic Bond: Created by the transfer of electrons from one atom to another, resulting in attraction of opposite charges.
  • Ions are formed by transfer of valence shell electrons.
  • Anion: gains one or more electrons.
  • Cation: loses one or more electrons.
  • Example: Sodium Chloride (NaCl)
• Covalent Bond: formed by the sharing of electrons between atoms.
  • Single Covalent Bond: one pair of electrons shared.
  • Double Covalent Bond: two pairs of electrons shared.
  • Triple Covalent Bond: three pairs of electrons shared.

Polar and Nonpolar Molecules

• Equal sharing of electrons produces electrically balanced nonpolar molecules.
• Unequal sharing of electrons produces polar molecules (e.g., water).
• Polar Covalent Bond: Unequal sharing, slight negative charge at one end, slight positive charge at the other.
• Nonpolar Covalent Bond: Equal sharing, charge is balanced among atoms.