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# MCAT Gen. Chem Ch. 1

Term | Definition |
---|---|

Proton | Has a positive charge and mass around 1 amu |

Neutron | Has no charge and mass around 1 amu |

Electron | Has a negative charge and a negative charge and negligible mass |

Nucleus | Contains the protons and neutrons, while the electrons move around the nucleus |

Atomic Number | Number of protons in a given element |

Mass Number | The sum of an element's protons and neutrons |

Atomic Mass | Equal to the mass number, the sum of an element's protons and neutrons |

Isotopes | Atoms of a given element (same atomic number) that have different mass numbers. They differ in number of neutrons. |

Three Isotopes of Hydrogen | Protium, Deuterium, Tritium |

Atomic Weight | Weighted average of the naturally occurring isotopes of an element. Periodic Table lists atomic weights, not atomic masses. |

Bohr Model Of The Atom | A dense, positively charged nucleus is surrounded by electrons revolving around the nucleus in orbits with distinct energy levels |

Quantum | Energy difference between energy levels which was first described by Planck |

Atomic Absorption Spectrum of An Element Is: | Unique. For an electron to jump from a lower energy level to a higher one, it must absorb an amount of energy precisely equal to the energy difference between the two levels. |

Atomic Emissions Spectrum | Spectrum that shows when electrons return from the excited state to the ground state, they emit an amount of energy that is exactly equal to the energy difference between two levels |

Quantum Mechanical Model | Posits that electrons do not travel in defined orbits but rather are localized in orbitals |

Orbital | Region of space around the nucleus defined by the probability of finding an electron in that region of space |

Heisenberg Uncertainty Principle | States that it is impossible to know both an electron's position and its momentum exactly at the same time |

Four Quantum Numbers | These numbers describe any electron in an atom |

Principal Quantum Number, n | Describes the average energy of a shell |

Azimuthal Quantum Number, l | Describes the subshells within a given principal energy level (s, p, d, and f) |

Magnetic Quantum Number, ml | Specifies the particular orbital within a subshell where an electron is likely to be found at a given moment in time. |

Spin Quantum Number, ms | Indicates the spin orientation (+ 1/2) of an electron in an orbital |

Electron Configuration | Uses spectroscopic notation to combine the n and l values as a number and letter respectively to designate the location of electrons |

(n+1) Rule | Electrons fill the principal energy levels and subshells according to increasing energy, which can be determined by the (n+l) rule |

Hund's Rule | Rule in which electrons fill orbitals. This states subshells with multiple orbitals (p, d, and f) fill electrons so that every orbital in a subshell gets one electron before any of them gets a second. |

Paramagnetic | Materials that have unpaired electrons that align with magnetic fields, attracting the material to a magnet. |

Diamagnetic | Materials that have all paired electrons, which cannot easily be realigned because they are repelled by magnets. |

Valence Electrons | Electrons in the outermost shell available for interaction (bonding) with other atoms |

Eq. 1.1: Planck Relation (Frequency) | E = hf. E = energy of quantum. h = Planck's constant, 6.626 x 10^-34 J*s. f = frequency of radiation. |

Eq. 1.2: Angular Momentum Of An Electron (Bohr Model) | L = nh / 2pi. n = principal quantum number. h = Planck's constant, 6.626 x 10^-34 J*s. |

Eq. 1.3: Energy Of An Electron (Bohr Model) | E = - RH / n^2. RH = Rydberg unit of energy, 2.18 x 10^-18 J / electron. n = principle quantum number. |

Eq. 1.4: Planck Relation (Wavelength) | E = hc / lambda. h = Planck's constant, 6.626 x 10^-34 J*s. c = speed of light in a vacuum, 3.00 x 10^8 m/s. lambda = wavelength of the radiation. |

Eq. 1.5: Energy Of Electron Transition (Bohr Model) | E = hc / lambda = - RH [1 / ni^2 - 1 / nf^2]. RH = Rydbergy unit of energy, 2.18 x 10^-18 J / electron. ni = initial principle quantum number. nf = final principle quantum number. |

Eq. 1.6: Maximum Number Of Electrons Within A Shell | 2n^2. n = principle quantum number. |

Eq. 1.7: Maximum Number Of Electrons Within A Subshell | 4l + 2 |

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SamB91