electronic configuration periodicity of elements l.
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ELECTRONIC CONFIGURATION PERIODICITY OF ELEMENTS. PERIODIC TABLE. Most powerful tool in the study of chemistry. Order the elements by Z number. Used to predict undiscovered elements and their properties. (Recall recent discoveries of atoms with Z = 113, 115)

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periodic table
PERIODIC TABLE
  • Most powerful tool in the study of chemistry.
  • Order the elements by Z number.
  • Used to predict undiscovered elements and their properties. (Recall recent discoveries of atoms with Z = 113, 115)
  • Periodicity is explained by quantum mechanics.
from h to multielectron atoms
From H to Multielectron Atoms
  • In H, AOs with the same n have the same E.
  • In multielectron atoms,
    • For a given set of QNs, orbital energies are lower than in H (larger Z value).
    • AOs with the same n value but different ℓ have different energies (nondegenerate).
    • orbitals with the same n and ℓ have the same E.
    • 3d and 4s have similar energies
determining electronic configurations
DETERMINING ELECTRONIC CONFIGURATIONS
  • There are four quantum numbers [n, ℓ, mℓ, ms] which have defined relationships to each other
  • These 4 QNs are used to define a set of atomic orbitals that electrons fill.
  • Aufbau (building-up) Principle determines the order of filling AOs; i.e. the electronic configuration of the atom.
electron config 2
ELECTRON CONFIG. (2)
  • Aufbau Prin. says that electrons fill AOs to achieve the lowest energy (atom’s ground state).
  • Electrons fill the lower energy AOs before filling the higher energy AOs.
  • Pauli Exclusion Principle: Max of 2 electrons per orbital; i.e. electron spins oppose and no two electrons can have the same 4 q.n. values in an atom.
electron config 26
ELECTRON CONFIG. (2)
  • Hund’s Rule: When filling orbitals of identical energy, fill the empty orbitals with one electron before pairing them up; I.e. maximize number of unpaired spins.
  • There are exceptions: e.g. 4s fill before 3d; Cr, Cu have a single 4s electron and fully- or half-filled 3d orbitals (extra stability).
  • Electron configs. of cations (remove from largest n AO) and anions (add according to Aufbau Prin.)
electron config 3
ELECTRON CONFIG. (3)
  • electron config, orbital-filling diagram, noble gas core for [the inner electrons] + valence electrons (VE).
  • VEs are the outermost electrons and the most important ones in chemical bonding.
  • Learn electron config.s through Kr; use PT to identify VEs of atoms beyond Kr. (Fig 5.17)
periodic law
PERIODIC LAW
  • Now we can see how the electronic configurations of atoms lead to periodicity of elements and form the basis for chemical and physical properties of elements.
  • PERIODIC LAW: When the elements are arranged according to Z, their physical and chemical properties vary periodically, regularly and predictably.
periodic law 2
PERIODIC LAW (2)
  • Elements in the nth A-Group (Main Group) have n electrons in the valence (outermost occupied) shell.
  • Elements in the nth period have n as the principal QN of its valence shell.
periodic law 3
PERIODIC LAW (3)
  • Fig 5.18 shows how the Periodic Table can be used to determine electron config.
    • Main Group: s- and p- block elements
    • Transition Group: d-block elements
    • Lanthanide and Actinide: f-block elements
  • Note filling order on p 186.
periodicity of atomic properties
PERIODICITY OF ATOMIC PROPERTIES
  • Atomic Radius, Size (Figs 5.1, 5.19, 5.20)
    • lower LH corner
  • Ionization Energy (Figs 6.3, 6.4, 6.5; Table 6.2) Atom (g) -----> Ion+(g) + electron
    • upper RH corner
  • Electron Affinity (Fig 6.6) Atom (g) + electron -----> Ion- (g)
    • upper RH corner
periodicity of atomic properties 2
PERIODICITY OF ATOMIC PROPERTIES (2)
  • Metallic Character
    • lower LH corner
  • Nonmetallic Character
    • upper RH corner
periodicity of atomic properties 3
PERIODICITY OF ATOMIC PROPERTIES (3)
  • Flame colors
  • Oxidizing agents (Group 7A)
  • Reducing agents (s-block)
  • Acidic Oxides (upper RH corner)
  • Basic Oxides (lower LH corner)
  • Amphoteric Oxides (in between)