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2: The Chemical Foundation of Life
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2.1: Atoms, Isotopes, Ions, and Molecules - Overview of Atomic Structure
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Atoms are made up of particles called protons, neutrons, and electrons, which are responsible for the mass and charge of atoms.
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2.2: Atoms, Isotopes, Ions, and Molecules - Atomic Number and Mass Number
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The atomic number is the number of protons in an element, while the mass number is the number of protons plus the number of neutrons.
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2.3: Atoms, Isotopes, Ions, and Molecules - Isotopes
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Isotopes are various forms of an element that have the same number of protons, but a different number of neutrons.
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2.4: Atoms, Isotopes, Ions, and Molecules - The Periodic Table
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Everything in the universe is made of one or more elements. The periodic table is a means of organizing the various elements according to similar physical and chemical properties.
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2.5: Atoms, Isotopes, Ions, and Molecules - Electron Shells and the Bohr Model
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Niels Bohr proposed an early model of the atom as a central nucleus containing protons and neutrons being orbited by electrons in shells.
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2.6: Atoms, Isotopes, Ions, and Molecules - Electron Orbitals
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Electron orbitals are three-dimensional representations of the space in which an electron is likely to be found.
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2.7: Atoms, Isotopes, Ions, and Molecules - Chemical Reactions and Molecules
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Chemical reactions occur when two or more atoms bond together to form molecules or when bonded atoms are broken apart.
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2.8: Atoms, Isotopes, Ions, and Molecules - Ions and Ionic Bonds
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Ionic bonds are attractions between oppositely charged atoms or groups of atoms where electrons are donated and accepted.
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2.9: Atoms, Isotopes, Ions, and Molecules - Covalent Bonds and Other Bonds and Interactions
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Covalent bonds result from a sharing of electrons between two atoms and hold most biomolecules together.
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2.10: Atoms, Isotopes, Ions, and Molecules - Hydrogen Bonding and Van der Waals Forces
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Hydrogen bonds and van der Waals interactions are two types of weak bonds that are necessary to the basic building blocks of life.
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2.11: Water - Water’s Polarity
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Water’s polarity is responsible for many of its properties including its attractiveness to other molecules.
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2.12: Water - Gas, Liquid, and Solid Water
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The orientation of hydrogen bonds as water changes states dictates the properties of water in its gaseous, liquid, and solid forms.
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2.13: Water - Heat of Vaporization
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Evaporation of water requires a substantial amount of energy due to the high heat of vaporization of water.
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2.14: Water - High Heat Capacity
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Water is able to absorb a high amount of heat before increasing in temperature, allowing humans to maintain body temperature.
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2.15: Water - Water’s Solvent Properties
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Water’s polarity makes it an excellent solvent for other polar molecules and ions.
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2.16: Water - Cohesive and Adhesive Properties
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Cohesion allows substances to withstand rupture when placed under stress while adhesion is the attraction between water and other molecules.
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2.17: Water - pH, Buffers, Acids, and Bases
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Acids dissociate into H+ and lower pH, while bases dissociate into OH– and raise pH; buffers can absorb these excess ions to maintain pH.
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2.18: Carbon - The Chemical Basis for Life
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Carbon is the most important element to living things because it can form many different kinds of bonds and form essential compounds.
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2.19: Carbon - Hydrocarbons
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Hydrocarbons are important molecules that can form chains and rings due to the bonding patterns of carbon atoms.
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2.20: Carbon - Organic Isomers
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Isomers are molecules with the same chemical formula but have different structures, which creates different properties in the molecules.
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2.21: Carbon - Organic Enantiomers
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Enantiomers share the same chemical structure and bonds but differ in the placement of atoms such that they are mirror images of each other.
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2.22: Carbon - Organic Molecules and Functional Groups
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Functional groups are groups of molecules attached to organic molecules and give them specific identities or functions.
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2.23: Synthesis of Biological Macromolecules - Types of Biological Macromolecules
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Biological macromolecules, the large molecules necessary for life, include carbohydrates, lipids, nucleic acids, and proteins.
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2.24: Synthesis of Biological Macromolecules - Dehydration Synthesis
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In dehydration synthesis, monomers combine with each other via covalent bonds to form polymers.
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2.25: Synthesis of Biological Macromolecules - Hydrolysis
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Hydrolysis reactions result in the breakdown of polymers into monomers by using a water molecule and an enzymatic catalyst.