Science

• The Quantum Mechanical Model of the atom describes the energies and positions of the electrons.
• The solid sphere is a model of the atom proposed by John Dalton.
• Joseph John Thomson discovered the electron and developed the "Plum Pudding or Raisin Bread Model" of the atom, where the atom was composed of a positively charged sphere where the electrons were loosely embedded on the surface.
• Ernest Rutherford discovered the protons and the nucleus.
• The Nuclear Model states that the atom consists of a dense positive center called the nucleus and is orbited by negatively charged electrons.
• Niels Bohr developed the Planetary Model of Atom, where electrons travel only in certain successively larger orbits.
• The Modern Theory of Atom describes the electron cloud as a "beehive" where the bees are the electrons moving around the nucleus in a cloud of energy levels.
• The Quantum Mechanical Theory describes the electron cloud as a "beehive" where the bees are the electrons moving around the nucleus in a cloud of energy levels.
• An abbreviated form of the electronic configuration makes use of the configuration of noble gas (Group 18).
• Hund’s Rule states that in filling up a set of degenerate orbitals such as the three 2p orbitals or the five 4d orbitals, the orbitals are occupied by one electron at a time with the electrons having the same spin, also known as parallel spin.
• The Aufbau Principle states that the electrons fill the orbitals, one at a time, starting with the lowest energy orbital then proceeding to the one with higher energy.
• The magnetic quantum number, m l, describes the orientation of the orbital in space and can have an integral value from -l to +l, including 0.
• If an atom is 'excited', for example, by being heated, one or more of its electrons may temporarily be transferred to an orbital of higher energy, but it will soon return to its ground state.
• The electron configuration of an atom describes how the electrons are distributed among the orbitals.
• The spin quantum number, m s, reveals that an electron behaves as though it spins about an axis like a toy top.
• The spin quantum number, m s, can only be +1/2 or -1/2.
• The Pauli Exclusion Principle states that no two electrons in the same atom can have the same set of four quantum numbers.
• Sublevel Orbital Shape can be 0 (spherical), 1 (dumbbell-shaped), 2 (4 cloverleaf-shaped), or 3 (dumbbell-shaped with a ring).
• The Quantum Mechanical Model of the atom describes the energies and positions of the electrons.
• The four quantum numbers that describe an electron within an atom are: n, l, m l, and m s.
• The principal quantum number, n, refers to the main energy level of an orbital and can have a value of any positive integer beginning with 1.
• To determine the maximum number of electrons that can occupy a main energy level, the 2 n 2 rule is followed.
• The maximum number of electrons for an n value of 1 is 2(1) 2 =2; that for an n value of 2 is 2(2) 2 = 8.
• The azimuthal quantum number, l, represents energy sublevels and can have values beginning with zero and increasing until the integer n - 1 is reached.
• The azimuthal quantum number also defines the shape of the orbital.