Hon. Chemistry Final Terms
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scarlett_haddy on May 31, 2010
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43 terms
Terms | Definitions |
|---|---|
 ground state | the lowest energy state of a system |
| excited state | a state that has higher energy than the round state of the system |
| Aufbau Principle | as protons are added one by one to the nucleus to build up the elements, electrons similarly are added to the atomic orbitals |
| Hund's Rule | the most stable arrangement of electrons in atomic subshells is the one with the greatest number of parallel spins; we fill orbitals singly before pairing |
| paramagnetic | attracted to a magnet; contains one or more unpaired electrons |
| diamagnetic | repelled by a magnet; contains only paired electrons |
| principle quantum number "n" | describes the principle energy level of the orbital and relates to the average distance of the electron from the nucleus |
| principle quantum number "l" | describes the shape of the orbital; values are "0" to "n-1"; value is designated by the type of orbital (0-s; 1-p; 2-d; 3-f) |
| magnetic quantum number "Ml" | describes the location of the orbital in space and the number of values indicates the number of orbitals; possible values are -l to +l |
| electron spin quantum number "Ms" | describes the rotation or spin of the specific electron; up (+1/2) or down (-1/2) |
| Heisenberg uncertainty principle | it is impossible to know simultaneously both the momentum and the position of a particle with certainty |
| Pauli exclusion principle | no two electrons in an atom can have the same four quantum numbers |
| Valence electrons | the outer elements of an atom, which are the ones involved in chemical bonding |
| Shielding effect | the decrease in attraction between an electron and the nucleus in any atom with more than one electron shell |
| effective nuclear charge (Zeff) | a charge felt by an electron (Zeff = Z - sigma) |
| atomic radius (AR) | one half the distance between the nuclei in two adjacent atoms of the same element in a metal. FOr elements that exist as diatomic unites, the atomic radius os one-half the distance between the nuclei of two atoms in a particular molecule |
| ionic radius | the radius of a cation or an anion as measured in an ionic compound |
| ionization energy (IE) | the minimum energy required to remove an electron from an isolated atom (or an ion) in its ground state |
| electronegativity (EN) | the ability of an atom to attract electrons toward itself in a chemical bond |
| ionic bond | the electrostatic force that holds ions together in an ionic compound - electrons are transferred form one atom to another (EN difference is greater than or equal to 2.0) |
| covalent bond | a bond in which two electrons are shared by two atoms (EN difference is less than or equal to 0.5) |
| polar covalent bond | a covalent bond with partial positive and negative charges due to the electrons spending more time in the vicinity of one atom than the other (EN difference is between 0.5 and 2.0, endpoints NOT included) |
| octet rule | an atom tends to form bonds until it is surrounded by eight valence electrons |
| VSEPER | Valence Shell Electron Pair Repulsion - pairs of electrons want to be as far away from the each other as possible |
| polar bond | a bond resulting in an even sharing of electrons. One end will be partially positive and the other will be partially negative |
| dipole moment | a molecule that has a positive and negative end |
| sigma bond | a covalent bond formed by orbitals overlapping end-to-end; its electron density is concentrated between the nuclei of the bonding atoms |
| pi bond | a covalent bond formed by sideways overlapping orbital; its electron density is concentrated above and below the plane of the nuclei of the bonding atoms |
| dispersion (London dispersion forces) | the attractive forces that arise as a result of temporary dipoles induced in the atoms or molecules |
| induced dipole | the separation of positive and negative changes in an atom (or a nonpolar molecule) caused by the proximity of an ion |
| dipole-dipole | forces that between polar molecules or a polar molecule |
| hydrogen bonding | a special type of dipole-dipole interaction between the hydrogen atom bonded to an atom of a very electronegative element (F, N, 0) and another atom of one of the three electronegative forces |
| ion-ion forces | the forces that hold two ions together or ionic bond, NOT an intermolecular force |
| network covalent forces | only applies to diamond, graphite, and quartz |
| triple point | the point at which the vapor, liquid, and solid states of a substance are in equilibrium |
| critical point | composed of a critical temperature and pressure |
| endothermic | processes that absorb heat from the surroundings |
| exothermic | processes that give off heat to the surroundings |
| enthalpy | (H) a thermodynamic quantity used to describe heat changes taking place at constant pressure |
| Hess's Law | when the reactants are converted to products, the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps |
| calorimeter | the measurement of heat changes |
| specific heat capacity | the amount of heat energy required to raise the temperature of one gram of a substance by one degree Celsius |
| Ksp (solubility product constant) | only one value for a given solid at a given temperature |
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