Uploaded August 2026 | Updated September 2026, 2 weeks ago
Chemistry Review Guide of Core Concepts
The Organizational Hierarchy of Biological Systems
Biological complexity emerges from hierarchical organization, each level governed by distinct physical and chemical principles.
Atom → quantum behavior, electron orbitals, chemical bonding
Molecule → emergent properties from atomic interactions
Cell → biochemical networks, compartmentalization
Tissue → cooperative cellular specialization
Organ → integrated physiological function
Organism → homeostasis, metabolism, signaling
Population → gene frequencies, evolutionary dynamics
Community → interspecies interactions, ecological networks
Ecosystem → energy flow, biogeochemical cycles
Biosphere → global systems biology
Protons, Neutrons, Electrons
Protons: positively charged
Determine the element
Neutrons: neutral
Affect mass and stability
Vary in isotopes
Electrons: negatively charged
Determine chemical behavior
Occupy quantized orbitals
Electron Cloud and Orbitals
Electrons do not orbit like planets, they exist in probability distributions called orbitals.
Types of orbitals:
s (spherical)
p (dumbbell)
d (clover)
f (complex)
How Electrons Fill Orbitals
Electrons fill orbitals according to:
Aufbau principle
lowest energy first
Hund’s rule
spread out before pairing
Pauli exclusion principle
max 2 electrons per orbital
Elements
An element is a substance where the atoms all contain the same number of protons (atomic number).
Atomic number uniquely identifies the element.
Changing proton number → completely different element.
Elements are arranged on the periodic table based on atomic structure and periodic trends.
Isotopes
An isotope is an atom of the same element that has a different number of neutrons.
Same protons → same element.
Different neutrons → different mass number.
Chemical properties remain nearly identical; physical properties (mass, stability) differ.
Isotopes enable:
Radiometric dating
Medical imaging
Metabolic tracing
Chemical Bonds and Biological Function
Covalent Bonds
Strongest biological bonds
Polar vs. nonpolar determines solubility and reactivity
Ionic Bonds
Strong in absence of water
Weakened in aqueous environments
Hydrogen Bonds
Directional, cooperative
Stabilize macromolecular structure
Van der Waals
Essential for molecular recognition
Enable gecko adhesion, protein packing
Why Valence Electrons Matter
Valence electrons control nearly every chemical property:
Bonding behavior: ionic, covalent, metallic
Oxidation states: how many electrons are lost or gained
Molecular geometry: VSEPR depends on valence electron pairs
Reactivity trends: metals lose valence electrons; nonmetals gain them
Periodic trends: ionization energy, electronegativity, atomic radius
Enzyme Catalysis
Increase reaction rate without altering equilibrium position.
Mechanism:
Bind substrate at active site
Stabilize transition state
Lower activation energy Ea
Key Points:
Enzymes accelerate both forward and reverse reactions
Do not change ΔG or equilibrium constant
Link to Lecture Slides: drive.google.com/file/d/1UgHRSP1HuiD-n1nnHH1hsq6lmArbtZnN/view?usp=drive_link
Due to the description character limit the full work cited for "Chemistry Review Guide of Core Concepts" can be viewed at... docs.google.com/document/d/1Hgybli36fMdxVtmfloWhryTuYS9PSRY0/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
Chemistry Review Guide of Core Concepts
The Organizational Hierarchy of Biological Systems
Biological complexity emerges from hierarchical organization, each level governed by distinct physical and chemical principles.
Atom → quantum behavior, electron orbitals, chemical bonding
Molecule → emergent properties from atomic interactions
Cell → biochemical networks, compartmentalization
Tissue → cooperative cellular specialization
Organ → integrated physiological function
Organism → homeostasis, metabolism, signaling
Population → gene frequencies, evolutionary dynamics
Community → interspecies interactions, ecological networks
Ecosystem → energy flow, biogeochemical cycles
Biosphere → global systems biology
Protons, Neutrons, Electrons
Protons: positively charged
Determine the element
Neutrons: neutral
Affect mass and stability
Vary in isotopes
Electrons: negatively charged
Determine chemical behavior
Occupy quantized orbitals
Electron Cloud and Orbitals
Electrons do not orbit like planets, they exist in probability distributions called orbitals.
Types of orbitals:
s (spherical)
p (dumbbell)
d (clover)
f (complex)
How Electrons Fill Orbitals
Electrons fill orbitals according to:
Aufbau principle
lowest energy first
Hund’s rule
spread out before pairing
Pauli exclusion principle
max 2 electrons per orbital
Elements
An element is a substance where the atoms all contain the same number of protons (atomic number).
Atomic number uniquely identifies the element.
Changing proton number → completely different element.
Elements are arranged on the periodic table based on atomic structure and periodic trends.
Isotopes
An isotope is an atom of the same element that has a different number of neutrons.
Same protons → same element.
Different neutrons → different mass number.
Chemical properties remain nearly identical; physical properties (mass, stability) differ.
Isotopes enable:
Radiometric dating
Medical imaging
Metabolic tracing
Chemical Bonds and Biological Function
Covalent Bonds
Strongest biological bonds
Polar vs. nonpolar determines solubility and reactivity
Ionic Bonds
Strong in absence of water
Weakened in aqueous environments
Hydrogen Bonds
Directional, cooperative
Stabilize macromolecular structure
Van der Waals
Essential for molecular recognition
Enable gecko adhesion, protein packing
Why Valence Electrons Matter
Valence electrons control nearly every chemical property:
Bonding behavior: ionic, covalent, metallic
Oxidation states: how many electrons are lost or gained
Molecular geometry: VSEPR depends on valence electron pairs
Reactivity trends: metals lose valence electrons; nonmetals gain them
Periodic trends: ionization energy, electronegativity, atomic radius
Enzyme Catalysis
Increase reaction rate without altering equilibrium position.
Mechanism:
Bind substrate at active site
Stabilize transition state
Lower activation energy Ea
Key Points:
Enzymes accelerate both forward and reverse reactions
Do not change ΔG or equilibrium constant
Link to Lecture Slides: drive.google.com/file/d/1UgHRSP1HuiD-n1nnHH1hsq6lmArbtZnN/view?usp=drive_link
Due to the description character limit the full work cited for "Chemistry Review Guide of Core Concepts" can be viewed at... docs.google.com/document/d/1Hgybli36fMdxVtmfloWhryTuYS9PSRY0/edit?usp=drive_link&ouid=104237452697237972847&rtpof=true&sd=true
