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Atomic Structure

• Matter: Anything that takes up space and has mass. Made of elements and compounds.

• Atom: Smallest unit of matter that retains properties of an element.

• Subatomic particles:

  • Protons: Positive charge (+), in nucleus.

  • Neutrons: No charge, in nucleus.

  • Electrons: Negative charge (-), form a cloud around nucleus.

• Atomic number: Number of protons in an element.

• Atomic mass: Sum of protons and neutrons.

• Isotopes: Atoms with same number of protons but different neutrons.

  • Radioactive isotopes: Nucleus decays, emitting particles/energy (useful for medical research).

• Electron shells: Energy levels around nucleus.

  • First shell holds 2 electrons.

  • Second shell holds 8 electrons.

• Valence shell: Outermost shell, determines bonding behavior.

• Energy levels: Electrons further from nucleus have more potential energy.

Deep Thoughts:

• Why is the atomic number important?

• How does the distribution of electrons affect an element's reactivity?

Chemical Bonds

• Covalent bonds: Atoms share valence electrons.

  • Single bond: 1 pair of electrons shared.

  • Double bond: 2 pairs shared.

  • Nonpolar covalent bond: Equal sharing of electrons.

  • Polar covalent bond: Unequal sharing, partial charges.

• Ionic bonds: Electrons transferred from one atom to another.

  • Cation: Positive ion (lost electron).

  • Anion: Negative ion (gained electron).

• Hydrogen bonds: Weak bond between partially positive hydrogen and electronegative atom (like O or N).

• Van der Waals interactions: Weak attractions due to transient charges.

Deep Thoughts:

• Why don’t noble gases form bonds?

• What makes hydrogen bonds weaker than covalent bonds?

Chemical Reactions

• Reactants: Starting materials in a reaction.

• Products: Resulting materials.

• Photosynthesis: Sunlight converts CO2 and H2O into glucose and O2.

• Chemical equilibrium: Rate of forward and reverse reactions is equal.

Deep Thoughts:

• Why is photosynthesis crucial for life on Earth?

• What happens when a chemical reaction reaches equilibrium?

Chapter 3: Water and Life

Properties of Water

• Polar molecule: Oxygen is more electronegative than hydrogen, creating partial charges.

• Hydrogen bonds: Intermolecular bonds between water molecules.

• Cohesion: Water molecules stick together (surface tension).

• Adhesion: Water molecules stick to other substances.

• Temperature moderation:

  • High specific heat: Absorbs/releases heat with small temperature change.

  • Heat of vaporization: Energy needed to convert water to gas.

  • Evaporative cooling: When water evaporates, the surface cools.

• Ice floats: Water expands upon freezing due to hydrogen bonds forming a crystalline lattice.

• Solvent of life:

  • Solution: Homogeneous mixture.

  • Solvent: Dissolving agent.

  • Solute: Substance dissolved.

  • Aqueous solution: Water is the solvent.

  • Hydrophilic: Water-attracting (polar/ionic).

  • Hydrophobic: Water-repelling (nonpolar).

• pH scale: Measures H+ concentration.

  • Acid: Increases H+ concentration.

  • Base: Reduces H+ concentration.

  • Buffer: Minimizes changes in H+ and OH- concentrations.

Deep Thoughts:

• Why does ice float on water?

• How does evaporative cooling help organisms maintain homeostasis?

• Why is water called the "universal solvent"?

Chapter 4: Carbon and Molecular Diversity

Carbon’s Role in Life

• Organic chemistry: Study of carbon-containing compounds.

• Carbon's versatility:

  • 4 valence electrons.

  • Forms 4 covalent bonds.

  • Can form chains, branches, rings, double bonds.

• Hydrocarbons: Molecules of only carbon and hydrogen (nonpolar, hydrophobic).

• Isomers:

  • Structural isomers: Differ in covalent arrangement.

  • Cis-trans isomers: Differ in spatial arrangement.

  • Enantiomers: Mirror images.

  • Diastereomers: Stereoisomers that are not mirror images and have different physical properties.

Functional Groups

• Hydroxyl (-OH): Polar, forms hydrogen bonds.

• Carbonyl (-CO):

  • Aldehydes: Carbonyl at end of carbon chain.

  • Ketones: Carbonyl within carbon chain.

• Carboxyl (-COOH): Acidic, can donate H+.

• Amino (-NH2): Basic, can pick up H+.

• Sulfhydryl (-SH): Forms disulfide bonds (important in protein structure).

• Phosphate (-PO4): Negative charge, involved in energy transfer (ATP).

ATP (Adenosine Triphosphate)

• Primary energy molecule.

• Consists of adenosine attached to three phosphate groups.

• Energy released when phosphate bonds are broken.