The Chemical Foundation of Life
2.1 Atoms, Isotopes, Ions, and Molecules: The Building Blocks
The Structure of the Atom
Atoms are made up of protons, neutrons, and electrons, which are responsible for their mass and charge.
Atomic Number and Mass
The atomic number is the number of protons in an element while the number of protons plus the number of neutrons determines the mass number.
Isotopes are different forms of an element that have the same number of protons, but a different number of neutrons.
The Periodic Table
The periodic table is a means of organizing the various elements according to similar physical and chemical properties.
Electron Shells and the Bohr Model
Niels Bohr proposed an early model of the atom as a central nucleus containing protons and neutrons being orbited by electrons in shells.
Electron orbitals are three-dimensional representations of the space in which an electron is likely to be found.
Chemical Reactions and Molecules
Chemical reactions occur when two or more atoms bond together to form molecules or when bonded atoms are broken apart.
Ions and Ionic Bonds
Ionic bonds are attractions between oppositely charged atoms or groups of atoms where electrons are donated and accepted.
Covalent Bonds and Other Bonds and Interactions
Covalent bonds result from a sharing of electrons between two atoms and hold most biomolecules together.
Water's polarity is responsible for many of its properties including its attractiveness to other molecules.
Water’s States: Gas, Liquid, and Solid
The orientation of hydrogen bonds as water changes states dictates the properties of water in its gaseous, liquid, and solid forms.
Water’s High Heat Capacity
Water is able to absorb a high amount of heat before increasing in temperature, allowing humans to maintain body temperature.
Water’s Heat of Vaporization
Evaporation of water requires a substantial amount of energy due to the high heat of vaporization of water.
Water’s Solvent Properties
Its polarity makes water an excellent solvent for other polar molecules and ions.
Water’s Cohesive and Adhesive Properties
Cohesion allows substances to withstand rupture when placed under stress while adhesion is the attraction between water and other molecules.
pH, Buffers, Acids, and Bases
Acids release H+ while bases release OH-; consequently, buffers maintain a system's required pH if exposed to these solutions.
Carbon is the most important element to living things because it's able to bond in many different ways and form many essential compounds.
Hydrocarbons are important molecules that can form chains and rings due to the bonding patterns of carbon atoms.
Isomers are molecules with the same chemical formula but have different structures, which creates different properties in the molecules.
Enantiomers share the same chemical structure and bonds but differ in the placement of atoms such that they are mirror images of each other.
Functional groups are groups of molecules that attached to carbon skeletons and give that molecule its specific identity or function.